Substance misuse is widespread among individuals with early-phase psychotic disorders and is associated with a worse illness course. Thorough assessment of patterns of substance misuse at admission for psychiatric care is often lacking and can compromise the accuracy of a diagnostic assessment that distinguishes between a primary psychosis and one that is substance induced. Given the risk to recovery from psychosis posed by substance misuse, close monitoring of the course and treatment of early-phase psychosis that is accompanied by substance misuse is indicated and could inform the development of more effective dual-diagnosis treatments.