Alzheimer's disease is the most commonly known neurocognitive disorder characterized by deterioration in areas such as memory, attention, and activities of daily living. From a behavioral perspective, memory and attentional deficits may be described as deterioration of stimulus control. This paper provides a case study of discrimination behavior in a patient with neurocognitive disorder. The purpose of the current study was twofold: (i) to study the effect of using presumed familiar pictures in arbitrary matching-to-sample tasks and (ii) to study variables that affect stimulus control in a patient diagnosed with vascular dementia. There were 12 conditional discrimination experimental conditions with various types of stimuli, from familiar pictures to identity matching. The results showed that the participant's responses were not in accord with experimenter-defined stimulus classes when using familiar pictures. However, intact stimulus control by sample stimulus was established following systematic procedural changes in the conditional discrimination tasks. Copyright © 2014 John Wiley & Sons, Ltd.