The aim of this study was to investigate cognitive biases in panic disorder patients via a questionnaire originally developed by Clark and co-workers [Clark, Salkovskis, Gelder, Koehler, Martin, Anastasiades, Hackman, Middleton & Jeavons, (1988). In Hand, I. and Wittchen, H.-U. (Eds) Panic and Phobias 2] to assess interpretations of ambiguous internal (bodily sensations) and external events. The results showed that, compared to normal controls, panic disorder patients interpreted bodily sensations in a more threatening fashion, while there was no difference concerning external events. Cognitive-behavioral treatments normalized this bias, and Cognitive Behavior Therapy and Applied Relaxation were equally effective in this respect. Moreover, compared to panicking patients, panic-free patients had reduced their cognitive threat bias at post-treatment and follow-up to a significantly larger extent. The results support the cognitive theory of panic disorder.