Objective: The aim of the present study was to determine sociodemographic and clinical characteristics, substance use patterns, psychosocial traumas, and gender differences among adolescent inpatients at an addiction treatment center. Method: Participants were 105 adolescents consecutively admitted and hospitalized at the Children and Adolescent Alcohol and Drug Dependency Research Treatment and Training Center of Bakirkoy Prof Dr. Mazhar Osman Training and Research Hospital for Psychiatry, Neurology, and Neurosurgery between February and December 2017. Kiddie-Schedule for Affective Disorders and Schizophrenia, present and lifetime version, Hamilton Anxiety and Depression Rating Scales, Conners-Wells’ Adolescent Self-Report Scale, Adolescent Dissociative Experiences Scale, Childhood Trauma Questionnaire, Addiction Profile Index-Practitioner Form, and Inventory of Parents and Peer Attachment were administered to all participants. Results: Of all cases, 31.4% were girls. Criminal history, a diagnosis of conduct disorder, substance use in the family, emotional abuse, and heroin use were frequently revealed. Among the girls, the substance use period was shorter and ecstasy use, traumatic experiences, diagnosis of post-traumatic stress disorder (PTSD) and severity of comorbidities were prominent; among the boys, synthetic cannabinoid use was more prevalent. While synthetic cannabinoid and alcohol use were frequent among the cases with a diagnosis of attention deficit hyperactivity disorder, heroin use was prominent among cases with depression diagnosis and ecstasy use among cases with PTSD. Conclusion: Among children and adolescents, substance use trends, childhood traumatic experiences, and severity of comorbidities may differ according to gender. It is important to take these differences into consideration in the treatment process.