Whereas it is well known that the ordering of items can influence research outcomes considerably, very little literature addresses instrument-order effects. Therefore, the aim of this study was to evaluate the effect of changing the administrative order of the Short-Form-12 (SF-12) and the Oral Health Impact Profile-49 (OHIP-49). It was hypothesized that if the SF-12 was administered first, the results would show poorer scores on the SF-12 subscales, as responses would not be restrained to only the oral impacts described by the OHIP-49. Using the Mann-Whitney U-test no significant instrument-order effects were found, except for the Psychological discomfort scale of the OHIP-49, where subjects scored higher when receiving the OHIP-49 first. However, the effect size was negligible (−0.08). These results suggest that no instrument-order effects occurred. Nonetheless, more research dealing with different instruments is needed. This study was performed within a dental setting and we recommend that instrument-order effects should be studied outside this domain.