In self reports, abstinent ecstasy/polydrug users claim that they experience certain ongoing affective and psychological changes including elevated anxiety, arousal, and depression. In addition, various aspects of cognition (e.g., everyday memory, reasoning, executive functioning) appear to be affected. The present paper investigated the link between these two psychological sequelae. Ninety-five ecstasy/polydrug users completed tests of reasoning, intelligence, information processing speed, executive functioning, and everyday memory. Affect was measured via a mood adjective checklist. Adverse effects attributed to ecstasy were measured via responses to adjectives reflecting changes in users since they started using the drug. In addition, indicators of sleep quality and daytime sleepiness were obtained. Users attributed a number of adverse effects to ecstasy, namely heightened irritability, depression, paranoia, and deteriorating health. Adverse effects were significantly and negatively correlated with aspects of intelligence, everyday memory, and sleep quality. Length of use of ecstasy use was positively correlated with adverse effects. While many users attribute a number of adverse affects to their use of ecstasy, it remains unclear whether these self-perceptions are a corollary of the psychopharmacological effects of the drug or reflect factors which in fact predate its use.