Hoarding can be a symptom of multiple neurological and psychiatric disorders, including obsessive-compulsive disorder (OCD). Recent evidence suggests that, in many cases, hoarding can also be a standalone problem that presents independently from other conditions; this has led to the proposal of a new diagnostic entity named hoarding disorder. This article reviews the neuropsychological and neuroimaging research on pathological hoarding. Most research in humans has been conducted in the context of individuals with brain damage, dementia, or OCD. Studies of well-characterized samples of individuals with hoarding disorder are extremely rare. Although not possible to establish firm conclusions at this stage, we conclude with a series of observations and recommendations for clinical practice. © 2011 Wiley Periodicals, Inc. J Clin Psychol: In Session 67:1–10, 2011.