One of the most common sexually transmitted infections in adolescents is human papillomavirus. These infections can occur in one or multiple areas of the female genitalia but the vulva is usually the initial site of implantation for HPV. We carried out a long-term follow-up study of adolescents to evaluate the incidence of single or multiple lesions in the lower genital tract, the correlation between sexual behaviour and their localisation and behavioural risk factors for persistence and recurrence of HPV lesions and cervical intraepithelial lesion (CIN). We interviewed 268 women aged 12-21 years who had previously had cytology and/or physical examination suspicious for HPV infection. We asked them information about their lifestyle, sexual behaviour, work, personal or family history of genital warts and school attendance. Those who smoked more than five cigarettes a day were considered "smokers". We have no specific data about oral contraception although we know that none of the patients had used oral contraceptives for more than two years. Two hundred and thirty-four young women between the ages of 12 and 21 years were included in the study. The diagnostic schedule for a complete evaluation included exo- and endocervical cytology, colposcopy and directed biopsy. We found that in 126 out of 234 (53.8%) adolescents using contraceptives, only 85 (36.3%) had used a condom. The sites most frequently affected by lesions were the vulva, perianus and perineum (194/234; 82.9%), and the cervix (125/234; 53.4%). Vaginal lesions were detected in only 29/234 patients (12.3%). In 161 patients, sexual habits, age at first intercourse (p = 0.68), frequency of intercourse (p = 0.49) and number of lifetime partners (p = 0.27) as well as age (p = 0.26) played a role in transmission and incidence of HPV infection but not in the location of the lesions. This could be due to coexistent clinical and subclinical multiple infections as well as transmission via intercourse or from other sources, including tampons. HPV infection is detected by abnormal pap test, but the low correlation with colposcopic and histological findings in this study justify the support of other examinations such as colposcopy and punch biopsy for diagnosis. Moreover more attention should be paid to the psychological aspect of diagnoses and treatment of adolescents compared to older women as there was a high rate of patients lost in our study: 75/234 (32.05%) before LASER surgery and 55/159 (34.59%) during follow-up. Only 12-45% of sexually active adolescent girls had obtained Pap smear screening. In our study we found no correlation between treatment failure and cigarette smoking or between the use of oral contraceptives and persistence/recurrence after LASER surgery.