The objective of this article was to estimate the prevalence, and identify the clinical correlates of comorbid substance misuse (abuse or dependence) among readmissions with schizophrenia, and particularly to establish whether comorbid substance misuse is associated with higher rates of depressive symptoms and suicidal ideation. Over 12 months, consecutive readmissions to an Irish psychiatric service with DSM-IV schizophrenia/schizoaffective disorder were assessed using clinical assessments of symptomatology including depression, insight and compliance. Comorbid substance misuse was diagnosed using DSM-IV criteria. Results: Of 102 readmissions 40% had lifetime, while 20% had current comorbid substance misuse and were predominately young males. Comorbid substance misuse had no statistically significant impact on positive, negative or depressive symptomatology. However, those currently misusing substances reported more suicidal ideation compared with past or non-substance misusers. The conclude that readmissions with comorbid substance misuse were more likely to report suicidal ideation, and may represent a group of individuals who are at higher risk of suicide.