In verbal protocol analysis, verbalization can occur either during decision making (concurrent data) or after (retrospective data). Although both methods have advantages and disadvantages, no empirical research has focused on a direct comparison. This study compared the effectiveness of concurrent and retrospective data for revealing the human decision making process. In general, the concurrent protocol analysis method outperformed the retrospective method. Not only was the number of concurrent protocol segments elicited higher than that of retrospective protocol segments, but concurrent data provided more insights into the decision-making steps occurring between stimulus introduction and the final choice outcome. However, retrospective protocols offer an interesting advantage: More statements about the final choice are provided in retrospective protocols than in concurrent protocols.