Background: Dual pathology (PD) is the superposition of a substance use disorder (TCS) and a psychiatric disorder (TP). Different studies have reported a prevalence of PD between 15% and 80%. The causal factor of drug use is unknown and may be related to intervening factors such as genetics, action of substances, group pressure, emotional problems, anxiety, and environmental stress. The psychiatric comorbidities most associated with the TCS are anxiety disorders, mood, post-traumatic stress psychotic disorders, behavioral disorders, personality disorders (especially antisocial personality), adaptive disorders, impulse disorders and defiant negativist disorder. Objective: To determine the prevalence of dual pathology (PD) in people with substance use disorders. Method: This is a descriptive prevalence study, which applied the MINI structured diagnostic interview to 133 patients with substance use disorder from April to December 2016. Descriptive statistics were applied. Results: The prevalence of dual pathology is 74.4%, the most prevalent disorders were: T. anxiety 56.4%, T. of humor 51.9%. T. antisocial 37.6% and T. psychotic 21.1%; 91.6% have alcohol consumption (ACT), 51.1% consumption of other substances (TCS) and 46.6% combination of both. Conclusions: There is a high prevalence of PT in the Institution, the most prevalent disorders are anxiety, humor and personality antisocial.