This study examined the prevalence and pattern of substance abuse among psychotic in-patients and relationships with diagnosis. Method:635 patients with diagnosis of schizophrenia, bipolar disorder and major depression were admitted to Kuwait Psychological Medicine Hospital over 6 months duration from the first of October 1998 to the end of March 1999. 47 patients with dual diagnosis were identified using DSM-IV criteria by two consultant psychiatrists. Cases with drug induced psychosis were excluded. Results:6 months prevalence rates for dual diagnosis were 6.2%, 10.3%, 3.2% for schizophrenia, bipolar disorder and major depression respectively. Patients with dual diagnosis were exclusively male. There was a trend among bipolar patients to abuse several substances more than other diagnostic groups. Conlusions: This study shows low rate of substance abuse among psychotic in-patients in Kuwait compared with high rate reported in Western countries. Factors responsible for this difference were discussed.