This study examined differences in frequency and severity of diurnal panic attacks between patients with (n = 22) and without (n = 21) a history of nocturnal panic attacks. Subjects were assessed with a modified version of the SCID, and completed daily panic attack diaries, the Anxiety Sensitivity Index, and the Fear Questionnaire. No differences were found between the groups in the actual number of expected or unexpected diurnal panic attacks experienced. Subjects in the nocturnal panic group experienced significantly more symptoms during diurnal panic attacks than did the diurnal only group. More specifically, the nocturnal panic group experienced more symptoms during expected diurnal panic attacks, but not during unexpected/spontaneous diurnal panic attacks. A greater proportion of the nocturnal panic subjects reported "chest pain" during diurnal panic attacks and a trend toward greater "fear of dying". Otherwise, the two groups were very similar. Implications of the findings are discussed in relation to the findings of other recent studies of nocturnal panic.