A 12-year-old daughter sprouting breasts doesn't want to see the same male pediatrician who has treated her since birth. Or a 13- year-old son whose voice has lowered balks at seeing a female doctor for his annual physical. Should he or she be accommodated?

"Yes," said one doctor who directs a large Boston-area pediatric practice.

"No," said another adolescent specialist who cares primarily for young girls.

If adolescence isn't easy, specializing in the field of adolescent medicine can be even more of a challenge. As this 10- year-old medical specialty matures, its practitioners are trying to broaden its mission beyond illnesses like eating disorders and addictions, and hoping to come to some consensus on how to reach healthy teenagers who seem increasingly adultlike.

With many teenagers not old enough to drive, vote or even pierce their ears, should they have the same patient confidentiality as adults, particularly in areas like birth control? Should they be paired with a same-gender doctor if they request it? Should teenagers be given freer access to Web sites with sexual-education content?

"Certainly the field has responded to the growing sophistication of teens in general," said Heather Munro Prescott, author of "A Doctor of Their Own: The History of Adolescent Medicine."

"Children are physically becoming adults at earlier ages and what were once considered adult behaviors are being adopted by lower and lower age groups."

With fewer than 500 doctors board-certified in adolescent medicine, most have focused their practices on young people who require special attention for problems such as anorexia or teenage pregnancy. But, increasingly, their research dollars are used to try to decipher the needs of all teenagers as they make the physical and emotional transitions into adulthood.

And, with the vast majority of the nation's teenagers in the care of pediatricians and general practitioners, pressure has increased on the relatively few specialists in adolescent care to help the general medical community deal with this age group.

"Doctors [who treat adolescents] have always had to work hard to build relationships with our patients," said Dr. Charles E. Irwin Jr., president of the Society of Adolescent Medicine. "And some of these questions can be difficult."

Gender issues often arise. According to Dr. Lawrence D. Cohan, director of a 10,000-patient pediatric practice in Boston and Quincy, about half of the youngsters seen by Milton Pediatrics Associates' eight physicians will request to change to a same-sex doctor once they are teenagers. "[Dr.] Rebecca Niloff and I tend to switch. Some of her boys come to see me. Some of my girls go to her."

"Occasionally," he said, "the request is from the parent. Mostly, it's what the kids want."

Irwin, who is also director of adolescent medicine at the University of California at San Francisco School of Medicine, said there is some anecdotal and survey evidence suggesting that teenage girls prefer women physicians. He also noted one limited recent study where a group of boys indicated some preference for female doctors as well, though, in general, boys who state a preference for a doctor by gender seem to prefer males.

Dr. Ann J. Davis, a specialist in pediatric and adolescent obstetrics and gynecology at Beth Israel Deaconess Medical Center, reviewed a study published this year in the Journal of Women's Health and Gender-Based Medicine, which concluded that women with male obstetrician-gynecologists were as satisfied with their provider as women with female ob-gyn doctors. At the same time, however, among women with female obstetrician-gynecologists, 63 percent said that the doctor's gender was an important factor.

"This was a very controversial piece for us," Davis said of publishing the study. "And the younger the woman, the stronger her preference for a female provider."

A doctor's gender, however, isn't important to all teenagers, according to Dr. Jonathan D. Klein of the University of Rochester School of Medicine and a leading researcher in the field of adolescent medicine. "In general, the issues around communication, respect and honesty tend to matter more than gender."

Klein said an increased reliance on the Internet for health information is a concern for doctors of all patients, particularly Web-savvy teenagers. A survey done by the Kaiser Family Foundation last year found that three out of four 15- to 24-year-olds have gone online seeking health information. That compares with 46 percent who checked sports scores, 50 percent who bought something, 67 percent who participated in a chat room and 72 percent who played a game online or downloaded music.

"It makes a lot of sense that this age group would use the Web for help," said Vicky Rideout, a vice president of Kaiser Family Foundation. "These tend to be sensitive issues, teens tend not to have established relationships with their own doctors and they spend a lot of time on the Web."

The report also underscored that many teenagers are blocked from finding information online by filter systems in place at schools, libraries and homes designed to block pornography sites.

Confidentiality is a tricky topic for doctors who see teenage patients. According to Irwin, studies show how profoundly adolescents want their conversations with their doctors to remain confidential, but many professionals find it impossible to promise confidentiality.

Dr. Robert Johnson, director of Adolescent and Young Adult Medicine at New Jersey Medical School, said he insists on spending as much time alone with his young patients as possible.

"Building this kind of trust is so important," Johnson said. He emphasizes the "young adult medicine" in his job description, hoping to bridge the gap between pediatric and adult care where many - especially males - lose regular touch with the medical profession.

"Young women will go to an [obstetrician-gynecologist] physician. I can have real difficulty transitioning my 25-year-old males" to primary-care doctors for adults, he said.

Dr. Estherann Grace, a specialist in adolescent medicine at Children's Hospital, said that establishing relationships with young patients is the key to caring for them now, as well as setting patterns that will help them to be solid health-care consumers in the future.

"Adolescents are like cats," she said. "They are very savvy. They know when their doctor is comfortable with them and it's absolutely critical."

[Charles E. Irwin Jr.], who is also director of adolescent medicine at the University of California at San Francisco School of Medicine, said there is some anecdotal and survey evidence suggesting that teenage girls prefer women physicians. He also noted one limited recent study where a group of boys indicated some preference for female doctors as well, though, in general, boys who state a preference for a doctor by gender seem to prefer males.

Dr. Ann J. Davis, a specialist in pediatric and adolescent obstetrics and gynecology at Beth Israel Deaconess Medical Center, reviewed a study published this year in the Journal of Women's Health and Gender-Based Medicine, which concluded that women with male obstetrician-gynecologists were as satisfied with their provider as women with female ob-gyn doctors. At the same time, however, among women with female obstetrician-gynecologists, 63 percent said that the doctor's gender was an important factor.

A doctor's gender, however, isn't important to all teenagers, according to Dr. Jonathan D. Klein of the University of Rochester School of Medicine and a leading researcher in the field of adolescent medicine. "In general, the issues around communication, respect and honesty tend to matter more than gender."