Aims: Mild cognitive deficits have been determined in both types of diabetes using neurocognitive tests. Little is known about the degree to which patients complain about their cognitive functioning. This study set out to investigate the magnitude and correlates of self-reported cognitive failure in adult out-patients with Type 1 and Type 2 diabetes. Methods: Subjective cognitive functioning was measured in 187 diabetic patients using the Cognitive Failures Questionnaire (CFQ). Demographic and clinical characteristics were retrieved from the medical records. The Patient Health Questionnaire 9 items (PHQ-9) was self-administered along with the CFQ to correct for the confounding effect of depression. Results: Analyses were based on 55 patients with Type 1 diabetes and 100 patients with Type 2 diabetes. No difference in mean CFQ score was observed between Type 1 and Type 2 diabetic patients or between Type 1 diabetic patients and healthy control subjects. Female patients with Type 2 diabetes reported significantly fewer cognitive complaints compared with female healthy control subjects. None of the demographic variables and diabetes-related complications was associated with subjective cognitive complaints. A strong positive association was found between depression symptomatology and frequency of self-reported cognitive failure. Conclusions: Our study could not confirm elevated subjective cognitive complaints in a group of Type 1 and Type 2 diabetes patients, as might be expected given the observed elevated rates of mild cognitive dysfunction in patients with diabetes. Self-reported cognitive failure appears largely determined by depressive symptomatology. Therefore, affective status should be included in any cognitive assessment procedure.