Recent research has suggested that the six-dimensional personality model, and especially the dimension Honesty-Humility/Integrity, adds incremental validity to the prediction of important criteria. We expected both this dimension and the dimension Conscientiousness to explain incremental variance in two academic criteria, namely grade point average (GPA) and counterproductive academic behaviour (CAB). In addition, we expected the more specific, so-called narrow traits of Conscientiousness and Honesty-Humility/Integrity to be stronger predictors of academic criteria than the broad traits. To test these expectations, two studies were conducted using the HEXACO Personality Inventory Revised (HEXACO-PI-R) and the Multicultural Personality Test-Big Six (MPT-BS). The results confirmed our expectations and suggest that academic criteria may be predicted with greater accuracy by focusing on the narrow traits of Conscientiousness and Honesty-Humility/Integrity. © 2010 John Wiley & Sons, Ltd.