This study explores the recently described phenomenon of Maladaptive Daydreaming (MD) and attempts to enhance the understanding of its features. It documents the experiences of 340 self-identified maladaptive daydreamers who spend excessive amounts of time engaged in mental fantasy worlds, in comparison to 107 controls. Our sample included a total of 447 individuals, aged 13âeuro"78, from 45 countries who responded to online announcements. Participants answered quantitative and qualitative questions about their daydreaming habits and completed seven questionnaires assessing mental health symptoms. Findings demonstrated that MD differs significantly from normative daydreaming in terms of quantity, content, experience, controllability, distress, and interference with life functioning. Results also demonstrated that Maladaptive Daydreamers endorsed significantly higher rates of attention deficit, obsessive compulsive and dissociation symptoms than controls. In sum, findings suggested that MD represents an under-acknowledged clinical phenomenon that causes distress, hinders life functioning and requires more scientific and clinical attention.