We examined the effects of object attributes on children's descriptive patterns in a referential communication task. Thirty preschoolers described object pairs that were selected by the experimenter. The targets were defined by shared size or colour, and differed on the non-target dimension in half of the trials. The children also completed a non-verbal reasoning task with analogous stimuli. They selected objects after observing the experimenter make a choice and inferring the basis for selection. In the communication task, the children produced fewer size than colour descriptions, particularly when the size targets differed in colour. They also over-specified colour features more often than size. They did not show a similar challenge identifying size relationships in the non-verbal task. The results support the conclusion that target attributes have a systematic influence on children's referential performance. Potential mechanisms for these effects, and directions for future research are discussed.