OBJECTIVES: The Perceived Deficits Questionnaire (PDQ) provides a self-report measure of cognitive dysfunction. The current work aims at assessing the psychometric properties of the PDQ adapted for MDD (PDQ-D). METHODS: A non-interventional, online panel survey with baseline assessment and 6-week follow-up of US and UK residents (aged ≥18 years) with and without MDD [diagnosed with depression by a physician and current Patient Health Questionnaire-9 (PHQ-9) score ≥10]. In addition to PDQ-D, the following instruments were included: Medical Outcomes Study Cognitive Functioning-Revised [MOS COG-R]; PHQ-9, Patient Global Impression of Severity [PGIS] and Change [PGIC]; SF-36 Health Survey [SF-36], Lam Employment Absence and Productivity Scale [LEAPS], Sheehan Disability Scale [SDS] and Work Productivity and Activity Impairment: Specific Health Problem [WPAI:SHP]. RESULTS: The study population consisted of 855 subjects at baseline (418 US and 437 UK), with MDD patients representing 49% of the sample in each country; 169 and 153 MDD patients were invited for the follow-up in the US and UK, respectively. Internal consistency was high for the total scale and for the four proposed subscales (Attention, Retrospective memory, Prospective memory, and Planning), with Cronbach’s alpha ranging from 0.81 to 0.96. Convergent validity was supported by strong correlations with other measures of cognitive functioning (0.8 Pearson’s coefficient) and moderate correlations with several construct measures known to be associated with cognitive functioning, including health-related quality of life, productivity at work, and other functional impairment (Pearson’s coefficients ranging from 0.3 to 0.6), and by substantial differences in scores in subgroups known to differ in cognitive functioning impairment. The PDQ-D was also responsive to changes in depression symptom severity. Confirmatory factor analyses supported the scoring of a global scale for perceived cognitive functioning. CONCLUSIONS: The PDQ-D is a reliable, valid and responsive instrument for assessing MDD patients’ perception of deficits related to cognitive functioning.