Our study on unplanned behaviour theory have examined the effect of booth recommendation system (BRS) on exhibition arise from either an extrinsic or intrinsic motivation. Previous studies, however, ignored the importance of the unplanned behavioural effectiveness through BRS that bonds extrinsic and intrinsic motivation together to deliver unexpected outcomes in exhibition. In this paper, we propose a model of the impact of BRS where perception of usefulness and threat to freedom of choice mediates the effect of both extrinsic and intrinsic motivation on unplanned booth visit behavior. We collected data from 101 visitors of exhibition and analyzed it using the Partial Lease Square (PLS) method. Our findings, interestingly, show that only intrinsic motivations (escape, attraction) significantly influence both perceived usefulness of BRS and threat to freedom of choice, however extrinsic motivation (information) does not significantly influences. Perceived usefulness of BRS mediates directly the effect of escape and attraction on unplanned booth visit behavior. The results and implications are further discussed.