This study was conducted with the aim of identifying the outcome and characteristics of patients admitted to acute psychiatric wards with a diagnosis of psychotic illness and substance misuse. In this multi-centre collaborative and opportunistic study, patients were allocated into four cohorts based on the type of drug use and then were followed up 1 and 6 months later. The total PANSS score improved significantly by the 6 month follow-up in all but the cannabis using cohort, which initially had the lowest symptom level. All cohorts improved significantly in levels of general symptoms, and three out of the four groups improved in the levels of positive symptoms (the cannabis and other drug cohorts were nearing significance at p=0.02). The biggest contrast between the groups was in the levels of negative symptoms. These improved only in the non-drug using cohort; however, even with this significant improvement, levels did not reach the lower levels initially evident in the cannabis only using cohort. Psychopathology and recovery processes of psychotic patients admitted to acute psychiatric wards will differ depending on their use of illicit substances. In particular, those who use cannabis but not other illicit substances are likely to have lower levels of negative symptoms.