OBJECTIVES: Obsessive-compulsive disorder (OCD) is a chronic mental disorder that is often hard to treat with current treatment options. Therapeutic outcomes are predicted by many factors, ranging from biological to psychosocial. Early life experiences and adult attachment influence the effectiveness of the treatment. This study explores their predictive abilities in the combined treatment of adult inpatients with OCD. METHODS: Seventy-seven patients with OCD, diagnosed according to the ICD-10 criteria, were included in the study, out of which 66 patients completed the treatment. All patients were previously unsuccessfully treated with a minimum of two antidepressants for three months each. They were evaluated with rating scales and questionnaires at the start and the end of a six-week hospitalization in a psychotherapeutic department. The treatment approach presented a combination of group cognitive-behavioural therapy and medication. RESULTS: The average severity of OCD, anxiety and depressive symptoms significantly decreased during the inpatient treatment. The improvement in Y-BOCS negatively correlated with the age of onset. The history of emotional abuse and neglect and physical neglect predicted a lower change in anxiety evaluated by a psychologist and perceived maternal care positively correlated with a decrease in anxiety assessed with a rating scale. Adult attachment anxiety predicted a lower decrease in the anxiety measured by the clinician but not the OCD symptomatology. Dissociative symptoms did not significantly predict a change in any of the measures. Comorbid personality disorder did not have a significant impact on therapeutic change. CONCLUSIONS: The early onset of the disorder was the sole predictor of the treatment outcomes regarding specific OCD symptomatology. Selected early adverse experiences, maternal care, and adult attachment anxiety predicted a change in the anxiety symptoms. Future research should focus on mediation and moderation analyses that could help target specific treatment strategies to decrease the impact of these factors.