The purpose of this study was to explore the relationships between performance on formal categorization-sorting tests and daily tasks that require sorting skills among individuals with schizophrenia compared with post-stroke and healthy control groups. Furthermore, the relationships among the performances of patients with schizophrenia on the various tests were studied. The study included 70 participants: 37 patients with schizophrenia treated at a community day center, 18 post-stroke patients, and 15 healthy controls. Subjects were evaluated on four different categorization tests (Wisconsin Card Sorting Test (WCST), Short Category Test (SCT), Loewenstein Occupational Therapy Cognitive Assessment (LOTCA), and Riska Object Classification (ROC); and five different functional daily tasks that require categorization abilities. Results showed significant differences between the performance of patients and control subjects on both tests and daily tasks. Spearman correlations within the schizophrenic group between test scores showed moderate significant correlations, and between tests and daily tasks showed low to moderate significant correlations. These findings suggest that weaker, yet significant relationships were found between performance on cognitive tests and daily tasks than between cognitive tests tapping the same or similar constructs. This type of difference would be expected; however, further research is needed to clarify the underlying components of categorization tests and their relations to daily task performance of individuals with schizophrenia.