Abstract Hoarding disorder is an under-recognized yet complex and pervasive psychological problem that dominates an individual's time, living spaces, relationships and safety. Hoarding behaviours have been associated with a number of disorders, including Obsessive-Compulsive Disorder (OCD), but as of yet, there has not been a systematic investigation of the presentation of hoarding phenomena across disorders. Simply—what do individuals with hoarding actually hoard, and does that differ from objects kept by people without hoarding? An understanding of the differential presentation of hoarding phenomena could help clarify the clinical status of hoarding disorder, which is currently under review. This study examined hoarding phenomena in 109 participants from five cohorts (individuals who hoard with and without comorbid OCD, individuals with OCD without hoarding, individuals with other Anxiety Disorders and non-clinical controls). The results supported the presence of hoarding symptoms across clinical and non-clinical cohorts, but some differences were apparent. In particular, individuals with hoarding disorder were far more likely than controls to collect idiosyncratic objects, some with deeply personal connections. Implications are discussed.