Several lines of evidence implicate the cholecystokinin B receptor (CCKBR) and the A2a adenosine receptor (A2aAR) in the etiology of panic disorder. To determine the roles each of these receptors may play in panic disorder, we have performed a mutation screen on the CCKBR gene using single strand conformation polymorphism (SSCP) analysis and sequencing. We identified two novel but rare substitutions in the same allele, [3263G>C; 3264A>G], located in the 3′-untranslated region of the CCKBR gene. We then analyzed 91 unrelated patients and 100 matched controls for the four confirmed polymorphic sites in the CCKBR gene and the 1083C>T polymorphism in the A2aAR gene. No evidence of association between the described variants and panic disorder was found. Our data therefore suggests that the CCKBR and A2aAR genes do not play major roles in the development of this disease.