Studies of the comorbidity of hypochondriasis have indicated high rates of cooccurrence with other anxiety disorders. In this study, the contrast among hypochondriasis, panic disorder, and social phobia was investigated using specific processes drawing on cognitive-perceptual models of hypochondriasis. Affective, behavioral, cognitive, and perceptual processes specific to hypochondriasis were assessed with 130 diagnosed participants based on the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, criteria (66 with hypochondriasis, 32 with panic disorder, and 32 with social phobia). All processes specific to hypochondriasis were more intense for patients with hypochondriasis in contrast to those with panic disorder or social phobia (0.61 < d < 2.67). No differences were found between those with hypochondriasis with comorbid disorders and those without comorbid disorders. Perceptual processes were shown to best discriminate between patients with hypochondriasis and those with panic disorder.