Purpose Item response time (RT) latencies offer a potentially promising approach for measuring faking in personnel testing, but have been studied almost exclusively as either long or short RTs relative to group norms. As such, the ability to reliably assess faking RTs at the individual level remains a challenge. To address this issue, the present study set out to examine the usefulness of a within-person difference score index (DSI) method for measuring faking, in which “control question” (baseline) RTs were compared to “target question” RTs, within single test administrations. Design/Methodology/Approach Two hundred six participants were randomly selected to simulated faking or honest testing conditions, and were administered two types of integrity test items (overt and personality), whereby group classification (faking/honest) served as the main dependent variable. Findings Faking condition RDs were longer than honest condition RDs for both item types (overt: d = .43; personality: d = .47), and overt item RTs were slightly shorter than personality item RTs in both testing conditions (honest: d = .34; faking: d = .41). Finally, using a sample cut score, the DSI correctly classified an average of 26% more cases of faking, and 53% less false positives, compared to the traditional normative method. Implications The results suggest that the DSI can be an advantageous method for identifying faking in personnel testing scenarios. Originality/Value This is the one of the first studies to propose a practical method for identifying individual-level faking RTs within single test administrations. Keywords Faking – Reaction time – Within person – Integrity – Selection.