Attentional impairment has been hypothesized to be associated with negative symptoms in schizophrenia. The present study examined the relation between attentional performance and positive and negative symptoms in both schizophrenic and manic patients. The results showed that deficits on the distraction conditions of a digit-span task were greatest in positive-symptom schizophrenics. Regression analyses revealed that only certain positive symptoms were related to digit-span scores; specifically, ratings of positive-thought disorder were inversely associated with performance for both schizophrenics and manics. The findings are discussed in light of their implications for conceptualizing the symptom categories and their laboratory correlates.