Introduction. Among patients with mental illness, dual disorders patients are characterized by a heterogeneous and more severe clinical presentation that is difficult to treat. Therefore, knowledge about the distribution of this disorder and the characteristics of these patients can be helpful to optimize and organize health resources. Objective. To explore the prevalence and socio-demographic and clinical factors associated with dual disorders patients who were hospitalized due to mental illness at a psychiatric unit in Colombia between January and June 2013; this data was collected and analyzed on the basis of the medical records of each patient. Method. Observational, quantitative, cross-sectional study of a secondary source. It included the analysis of 201 patients aged 18 to 65. Results. There were 201 patients analyzed; 45.3% had dual disorders, with a ratio of 2.24 men:women; there was a high frequency of single marital status (69.2%) and more than 90% had a low socioeconomic level. The factors significantly associated with dual disorders in order of importance were: age from 18 to 35 years (OR = 11.03; CI 95% [4.43, 27.46]), male (OR = 5.10, CI 95% [2.26, 11.50]), history of aggression (OR = 3.35; CI 95% [1. 63, 6.91]), and readmission in the year after hospital discharge (OR = 2.23; CI 95% [1.08, 4.61]). Discussion and conclusion. Dual disorders prevalence in this study is similar to that found by other authors. The high prevalence of dual disorders requires specialized therapeutic programs for treatment. The more hospitals know about the associated variables in this study, the more they will be able to improve their approach to patients.