Background Subjective cognitive complaints are generally poorly associated with objective memory functioning in older persons. Subjective cognitive decline (SCD) is a key feature in SCD and amnestic mild cognitive impairment (aMCI) which both can represent early Alzheimer's disease (AD). The aim of this study was to assess how memory clinic patients with SCD, MCI and mild AD dementia scored on 3 different complaint measures and if the format of assessment had an impact on the association with cognitive functioning, age, and depressive symptoms. Methods We included 17 SCD patients, 17 aMCI patients, 17 patients with mild AD, and 30 controls. Complaints were assessed with the Cognitive Change Index (CCI), the Subjective Memory Complaints (SMC) scale, and the Memory Complaint Questionnaire (MAC-Q). Results There were no significant differences between the total scores in the patient groups on the questionnaires. However, significant differences were found in the number of patients classified with impairment when using the CCI, the SMC, and the MAC-Q. Scores on all questionnaires were significantly associated with depressive symptoms, and significant associations with age, gender, and Addenbrookes Cognitive Examination score were found for the SMC. In patients with cognitive dysfunction, lower memory awareness significantly predicted fewer cognitive complaints. Conclusions SCD patients in a memory clinic setting report the same degree of cognitive impairment as patients with aMCI and mild dementia, and in a hospital-based cohort we extend previous findings from healthy controls, that definition of SCD may depend on the format of assessment.