Patients with the behavioral variant of frontotemporal dementia have marked impairment in everyday life, yet little is known about factors underlying this impairment. Moreover, a recently identified subgroup with normal brain imaging has an excellent prognosis (phenocopy cases) and their performance on activities of daily living (ADL) tasks is unknown. Eighteen behavioral variant frontotemporal dementia patients were assessed on 2 ADL measures, the Disability Assessment for Dementia, a caregiver-based interview, and the Assessment of Motor and Process Skills, a performance-based instrument. Behavior change, global cognition, executive function, and magnetic resonance imaging brain atrophy were also evaluated. There was no association between the 2 ADL measures. A model combining the Addenbrooke's Cognitive Examination Revised (global cognition) and Frontal Systems Behavior Scale (frontal dysfunction) explained the variance on ADL performance. A qualitative rating distinguished between pathologic and phenocopy patients better than the performance-based assessment. Degree of frontal dysfunction and overall dementia determined the level of ADL impairment. The phenocopy patients were clearly distinguishable when evaluated using a performance-based, and even better with a qualitative rating assessment.