This study investigates the electrophysiological and behavioral correlates of cannabis use disorder (CUD), using resting state EEG and cognitive tasks. Electrophysiologically, chronic cannabis-users demonstrated elevated levels of alpha rhythm, together with increased synchronization across the whole scalp. Behaviorally, no significant group effects were detected, but a correlation was found between attentional impairment and increased EEG spectral power. As this signature was absent in the non-user group, CUD-associated patterns of neural activity might be causally related to the cognitive impairments. These findings suggest there may be reduced cortical activation associated with cannabis use, although the study's correlative design is unable to determine whether this is a cause or consequence of cannabis use.