It has been suggested that chemotherapy treatment for cancer may contribute to cognitive decline in older cancer survivors. This issue is particularly important given that subtle cognitive impairment, particularly in cognitive processing speed, can affect functional status and quality of life for older adults. Multivariate regression of data from a longitudinal randomized controlled trial of older adults revealed a trend towards decreased performance after cancer treatment with chemotherapy on several functional measures associated with processing speed (as compared with matched individuals who did not have cancer). Additional analyses revealed that a subset of the chemotherapy-treated adults demonstrated a reliable negative change on several measures of processing speed. While inconclusive, this hypothesis generating work suggests that cognitive dysfunction following cancer treatment may contribute to disability observed in older cancer survivors. Further research is needed to determine the significance of the relationship between cognitive and functional impairment in older cancer survivors. © 2009 Blackwell Publishing Ltd.