In psychotherapy, there is a rising need to evaluate the therapeutic process and outcome quality. However, the effort for documentation binds manpower and is a burden on economic resources. Hence, we studied the usability of a new by developed, mobile, computer-assisted basis assessment (ComBas 1.3) in comparison with paper-and-pencil versions with respect to its effects on data structure and cost reduction. More than 9000 standardised psychometric tests (personality inventory: Giessentest, complaint checklist: Giessener Beschwerdebogen, mood checklist: Berliner Stimmungsfragebogen) were applied with each method to 1400 psychosomatic patients. It was found that usage of the mobile computer-assisted assessment reduced the time by 2/3 spent on documentation, because data organisation and accessibility for clinical, scientific, and educational needs were significantly improved. Moreover, no differences in stability coefficients and data distribution were seen between the two methods. In trait variables, there was also an equivalence in scale means, but in state variables, especially in complaint scales, we identified a tendency toward higher scale means in computer-assisted measurement. We cannot establish whether this is only a methodical effect or is additionally influenced by changes in samples during the evaluation period between 1989 and 1996. Hence, we concluded that comparison samples for state instruments should be adjusted to the applied test form and actualised for use in individual diagnostics.