Human papillomavirus is a common sexually transmitted virus, and persistent infection with high-risk types is the necessary factor for cervical cancer. We investigated sexual behaviour and the age of the first sexual intercourse among young people (14-24 years) in Liguria (Northern Italy) in order to provide information that might orient the country's future vaccination policy. The Italian Authorities offer free vaccination to 12-year-old females, however a better prevention of HPV would to be implemented by introducing the vaccine to new cohorts of females after the first year of the vaccination campaign. Our survey was carried out from 1st May 2006 to 31st December 2007 and involved 3474 volunteers. We administered a written questionnaire to students (14-24 years) and workers (20-24 years). The median age+/-MAD of the sexual debut was 15+/-1 for both females and males in students group and 16+/-1 for both males and females in workers group. This study provides evidence that many Ligurian adolescents have their first sexual experience at a very early age, and often without protection against sexually transmitted diseases. Furthermore, a large percentage of all age-groups are sexually active and have multiple partners. The aim of this study was to identify those cohorts of females to whom vaccination should be offered free of charge. To this end, we calculated the percentage of infections that could be avoided by vaccination in each age-class: the younger the subjects, the higher the number of preventable infections. Our findings suggest that current HPV vaccination should be implemented by introducing new cohorts, especially young girls (14-16 years).