Deciding how to approach a word problem for solution is a critical stage of problem solving, and is the stage which frequently presents considerable difficulty for novices. Do novices use the same information that experts do in deciding that two problems would be solved similarly? This set of four studies indicates that novices rely more on surface feature similarity. However, when certain aspects of the problem structure were held constant, novices correctly identified problems that would be solved similarly significantly more often. The results suggest: (1) the distinction of surface and deep features may not be rich enough for describing categorization of word problems, and (2) novice problem solvers are capable of recognizing some similarities of problem structure. A third level of classification of word problems is proposed to explain these results. (Author)