['This study evaluated serum levels of the neuropeptides calcitonin gene-related peptide (CGRP) and substance P (SP) in coronary artery disease (CAD) patients with and without a history of diabetes mellitus (DM).', 'Patients undergoing coronary angiography for suspected myocardial ischaemia were divided into four groups depending on their clinical status: control group (no CAD or DM; n=44), DM group (DM without CAD; n=46), CAD group (stable CAD without DM; n=44) and DM+CAD group (stable CAD with DM; n=50). Serum levels of CGRP and SP were determined using radioimmunoassays.', 'CGRP and SP levels in the DM and CAD groups were significantly lower than in the control group. The lowest levels of CGRP and SP were observed in the DM+CAD group. There were no significant differences in CGRP and SP levels between the DM group and the CAD group.'] Are serum levels of calcitonin gene-related peptide and substance P decreased in patients with diabetes mellitus and coronary artery disease?