The objective of this study was to investigate the clinical predictors of response to treatment with selective serotonin reuptake inhibitors (SSRI) in a sample of patients with obsessive–compulsive disorder (OCD). A total of 55 patients diagnosed as OCD according to revised 3rd edition of the Diagnostic and Statistical Manual of Mental Disorders criteria underwent a 12-week standardized SSRI treatment. According to ‘treatment response’, defined as at least a 35% drop in the Yale–Brown Obsessive–Compulsive Scale total score, OCD patients were divided into two groups. A total of 32 (58.2%) patients who responded to treatment and 23 (41.8%) who did not, were compared in terms of sociodemographic and clinical characteristics. The authors' findings demonstrated that the severity of obsession–compulsions and disability in work, social and family lives at the beginning of treatment were significantly higher in OCD patients who did not respond to treatment in comparison to those who did. Linear regression analysis, however, revealed that Sheehan Disability Scale-work score at baseline was a predictor of response to SSRI treatment. The higher levels of disability at the beginning of treatment in patients with OCD are associated with a poorer response to SSRI.