For this study, university students were asked to create a collage using circular and square pasteboards. Focusing on the impressions the participants obtained from the shapes of the pasteboards for collage expression, this study examined if it were related to self-understanding. In addition, the usability of collage using circular pasteboards was examined. The participants' impressions were different between the two types of pasteboards, and also a different degree of self-understanding was acquired from collage expression and creation depending on the shape of the pasteboard. Circular pasteboards can be useful because it facilitates the ideas and imagination of creators and enables free expression.