Dimensional expressions are regarded as linguistic reflections of spatial cognition. By contrastive analysis of German and Japanese constructions using dimensional expressions, it is revealed that there are three functions associated with dimensional expressions: identification, norm-related comparison and non-norm-related comparison. These three functions are based on different ways of perceiving spatial objects, but for their linguistic realization the existence of certain grammatical constructions, especially the adjectival and the nominal, together with their markedness, plays an important role. In both languages, individual dimensional expressions are essentially characterized by cognitive parameters. German expressions are mostly explored in terms of the parameter, but certain Japanese expressions require additional conditions for lexicalization. This difference is mainly based on the different strategies taken by German and Japanese respectively: the observer-based (O) strategy and the proportion-based (P) strategy (Lang 2001). O terms are mostly free from selectional restrictions, but P terms often involve some restriction regarding the shape of the object. It is assumed that such restrictions are related to the cognitive saliency of the term, and a saliency hierarchy of dimensional parameters is proposed.