Lower extremity peripheral artery disease (PAD) is a powerful predictor of cardiovascular events and mortality. The ankle-brachial index (ABI) is an objective and standard diagnostic method to diagnose PAD (an ABI ≤ 0.9 is considered pathological). The American Heart Association (AHA) and the American College of Cardiology (ACC) recommend using both the posterior and anterior tibial arteries when assessing ABI. We investigated whether there was a difference in the diagnosis of PAD if the ABI was measured in the posterior or the anterior tibial arteries. The results showed that among participants with ABI ≤0.9, between 30% and 40% would not get a PAD diagnosis if the ABI was measured in only 1 of the arteries. In conclusion, this study emphasizes the importance of measuring the ABI in both the posterior tibial and the anterior tibial arteries when diagnosing PAD.