Previous studies have noted the paradox of the dually-diagnosed (serious mental illness and substance abuse) in which the dually-diagnosed are judged to be both behaviorally more disorganized and simultaneously more socially competent. This study sought to further assess this paradox with a large sample size and a comprehensive assessment approach. In this study, the dually-diagnosed (N = 233) differed significantly from the non-dually-diagnosed (N = 262) in the symptom paradox. The dually-diagnosed were judged both more behaviorally disorganized and socially intact. The comprehensive assessment approach yielded empirical data in support of three possible hypotheses to explain the paradox. The implications of the findings and the three possible hypotheses are discussed.