BACKGROUND Although hoarding symptoms have been traditionally conceptualized as part of obsessive-compulsive disorder (OCD), recent data suggest that they may be more closely related to attention-deficit hyperactivity (ADHD) symptoms and, in particular, inattention. The aim of the present epidemiological study was to investigate the association between retrospectively reported ADHD symptoms in childhood and lifetime hoarding symptoms. METHODS Retrospectively reported childhood ADHD, and lifetime hoarding and obsessive-compulsive symptoms were assessed with the Composite International Diagnostic Interview 3.0 in a random subsample of individuals (n = 2,963) participating in a cross-sectional survey of the adult general population of nine European countries, as part of the World Mental Health (WMH) Surveys. RESULTS Lifetime hoarding symptoms were more common among individuals with childhood ADHD symptoms than those without ADHD symptoms (8.9% versus 2.7%, P = 0.024). Childhood inattention (but not hyperactivity) was associated with lifetime hoarding symptoms (OR = 6.04, 95% CI = 3.59-10.1) and this association remained significant after controlling for the presence of obsessive-compulsive symptoms. CONCLUSION Longitudinal studies are now needed to explore the hypothesis that inattention symptoms in childhood may be a precursor of hoarding difficulties later in life.