Introduction: Chronic use of psychoactive substances has been associated with various cognitive impairments. Also, it has been described that an associated cognitive impairment is one of the long-term consequences of having a mental illness. The coexistence of an addiction with at least one other mental illness is quite frequent. Little has been published about cognitive impairments in dual diagnosis patients in Colombia. Methods: A cross-sectional descriptive study with primary data was carried out in 31 patients with a dual diagnosis who were admitted to the Centro de Atención de Patología Dual (Dual Diagnosis Care Center) of the Clínica del Oriente between June and December 2017. The psychiatric diagnostic criteria of DSM-IV-TR and neuropsychological tests were used. Results: It was found that 90.9% of the patients had alterations in the medial orbital cortex; 54.5% in the anterior prefrontal cortex; and 45.5% in the dorsolateral cortex; 72.7% had alterations in sustained attention; 59.1% in alternating attention; and 81.8% in executive functions. Conclusions: 100% of patients with dual pathology suffer from cognitive impairments, which pose significant challenges in their rehabilitation process. For this reason, the inclusion of neuropsychological therapies should be considered in addition to comprehensive management.