This study investigates the effect of "preactional self-regulation" on the quality of problem solving. The experimental study was realized in a problem-based self-regulated learning environment. Data of 78 participants on externalized mental models, re-representing the problem solutions, were collected. A computer-based analysis tool was utilized to determine the congruence between the participant's and an expert's solution. This allowed capturing, quantifying, and comparing the quality of the participants' problem solution. Results show that an initiated phase of "preactional self-regulation" leads to a higher quality of problem solution. However, findings show no significant differences between experimental and the control groups.