<b><i>Introduction:</i></b> The added diagnostic value of ¹¹C-PiB-PET for the assessment of the accumulation of cortical beta-amyloid in memory clinic patients with uncertain diagnosis remains undetermined. <b><i>Methods:</i></b> All patients who underwent PiB-PET at the Copenhagen Memory Clinic between March 2008 and November 2011 were included in this uncontrolled, retrospective study. The standard diagnostic evaluation program included physical and neurological examination, cognitive and functional assessment, a cranial CT or MRI, functional imaging and cerebrospinal fluid sampling. Based on anonymized case reports, three experienced clinicians reached a consensus diagnosis and rated their confidence in the diagnosis before and after disclosure of PiB-PET ratings. PiB-PET scans were rated as either positive or negative. <b><i>Results:</i></b> A total of 57 patients (17 females, 30 males; age 65.7 years, range 44.2–82.6) were included in the study. Twenty-seven had a positive PiB-PET scan. At the first diagnostic evaluation, 16 patients were given a clinical Alheimer’s disease diagnosis (14 PiB positive). Of the 57 patients, 13 (23%) were diagnostically reclassified after PiB-PET ratings were disclosed. The clinicians’ overall confidence in their diagnosis increased in 28 (49%) patients. <b><i>Conclusion:</i></b> PiB-PET adds to the specialist clinical evaluation and other supplemental diagnostic investigations in the diagnostic classification of patients with uncertain diagnosis in a specialized memory clinic.