Objective: to analyze the behavior and infractional acts of 26 female adolescents. Method: a descriptive, sequential explanatory, mixed study, conducted in an educational center in Northeastern Brazil. A questionnaire was applied including sociodemographic; gynecological/obstetric; behavioral variables as well as variables referring to infractions and institutional incarceration. The Statistical Package for Social Sciences version 23.0 was used for data analysis, descriptive analysis, frequency distribution for categorical variables and calculation of measures of central tendency for numerical variables. In the qualitative stage, data were collected through in-depth interviews, which aimed to interpret quantitative analysis variables. The interviews were recorded and transcribed in full, the data were coded and grouped into themes. Pre-analysis, exploration of the collected material, treatment of the results and interpretation were performed. Thematic analysis was used to identify the core meaning that makes up the communication, whose presence or frequency have some meaning for the object studied. Results: the age ranged from 12 to 18 years and 26.9% attended school. The most frequent offenses were theft (61.5%) and homicide (19.2%). The use of alcohol and illicit drugs, was reported as 53.8% and 46.2%, respectively. All reported being sexually active and 96.2% had had more than one sexual partner in their lives. Seven had already become pregnant, and four of these decided to have abortions. Six (23.1%) declared themselves as bisexual and five (19.2%) as homosexuals. The adolescents mentioned the need for homosexual relations at the place of detention, due to the prohibition of conjugal visits. Conclusion: adolescents who are deprivation of liberty have high social vulnerability.