Impact statements are increasingly required and assessed in grant applications. In this study, we used content analysis to examine the 'comments on impact' section of the postal reviews and related documents of Science Foundation Ireland's Investigators' Programme to understand reviewers' "ex ante" impact assessment. We found three key patterns: (1) reviewers favoured short-term, tangible impacts, particularly commercial ones; (2) reviewers commented on process-oriented impact (formative) in a more concrete and elaborate manner than on outcome-oriented impact (summative); and (3) topics related to scientific impacts were widely discussed even though the impact section was to be used for evaluating economic and societal impacts. We conclude that for "ex ante" impact assessment to be effective, funding agencies should indicate the types of impact expected from research proposals clearly instead of a general 'wish list' and that more focus should be put on process-oriented impact than outcome-oriented impact.