The aims of this study were to identify dimensions of reasons for adherence and nonadherence to antipsychotic medications, and their associations with clinical and demographic profiles. A total number of 106 participants with DSM-IV psychosis spectrum disorders from two larger studies in inpatient and community settings participated. The Rating of Medication Influences (ROMI) Scale was used to measure subjective reasons for adherence and nonadherence. A series of multiple regression analyses found that mood symptom scores on the Positive and Negative Syndrome Scale (PANSS) predicted most dimensions of reasons for adherence and nonadherence. Higher mood scores were associated with positive affinity for medications and positive relationship with clinicians. Lower mood scores predicted four out of five reasons for nonadherence. Adherence and nonadherence behaviors were determined by different variables and were not mirror opposites.