Three experiments are reported which examined the role of geometry and functional relations in the comprehension of the spatial prepositions over, under, above, and below. The tasks used consisted of rating how appropriate sentences (containing one of these prepositions) were to describe a series of pictures. For example, the pictures comprised a person holding an object with the function of protection from falling objects (e.g., an umbrella). Each picture was depicted with the object shown as fulfilling its function or not at different geometric positions. The results of Experiment 1 show a significant effect of functional relations on the ratings given. However, while over/under were very sensitive to functional relations, above/below were more influenced by geometric relations. The second experiment replicates these effects with objects depicting noncanonical functions (e.g., a suitcase sheltering someone from rain). Experiment 3 manipulated frame of reference and found evidence for conflict of frames of reference effects on the rating of above/below, but not in the same way for over/under. Conversely the ratings of over/under were found to be affected by functionality while those for above/below were not. These results indicate for the first time that spatial prepositions are differentially influenced by geometric and functional relations.