We investigated the relationship between peripheral artery disease (PAD) and coronary artery disease (CAD) complexity in patients with acute coronary syndromes (ACS). Consecutive patients with first time diagnosis of ACS (n = 150) were enrolled. SYNTAX score (SS), a marker of CAD complexity, was assessed by dedicated computer software and diagnosis of PAD was established by ankle-brachial index (ABI) value. SYNTAX score was higher in patients with overt and borderline PAD (ABI ≤ 0.99) than normal participants (ABI 1-1.29; 16.7 ± 8.2 vs 10.1 ± 5.5; P < .001). In addition, there was a strong negative correlation between ABI and SS (r = -.46; P < .001).We have demonstrated increased CAD complexity in patients with ACS and PAD and strong correlation between degree of PAD and coronary lesion complexity.