Canine cognitive dysfunction (CCD) is a neurobehavioural syndrome affecting aged dogs. Using a large cross-sectional epidemiological study of older dogs, this study aimed to estimate the prevalence of CCD amongst community based dogs (mean age 11.67years; range 8-19.75) and to determine the rate of veterinary diagnosis amongst affected dogs. An 84-item questionnaire was used to obtain information across six behavioural domains. Of the eligible survey responses obtained (n=957) a randomly selected one-half (n=497) was used for this study. Using a provisional diagnosis based on 27 significant behavioural items, the prevalence rate of CCD was estimated to be 14.2%. This was in contrast with only 1.9% diagnosed with CCD by a veterinarian. There was an exponential increase in prevalence of CCD with age (R2=0.9435), but prevalence did not differ by breed size or between longevity groups. The prevalence rate of CCD reported here is consistent with previous findings, and further supports the contention that the majority of these dogs do not receive a formal diagnosis.