Using the ‘remember-know’ (R-K) procedure (Tulving, 1985), with the additional ‘guess’ (G) response option (Strack & Froster, 1995), the present study was designed to help answer questions regarding the effects of perceptual similarity on false recognition in young and old adults. New words were tested under two conditions: perceptually similar (presented in studied fonts) or perceptually dissimilar (presented in novel fonts). There were two old adult groups and one young adult group. Each word in the study phase was presented twice, randomly spaced apart to one old adult group (old-spaced-repetition) and the other (old non-repetition) received identical encoding condition to the young group, which involved each word at the study phase being shown only one time. The old-spaced-repetition group was included as a control group. Kornell, Castel, Eich, and Bjork, (2010) found that both young and old adults benefitted from spaced-repetition at the study phase. Therefore, if levels of hits between young and old-spaced-repetition groups were comparable and if levels of false alarms for the old non-repetition group were higher than the young group, the current study would find clear effects of perceptual similarity on false alarms in normal cognitive ageing. However, the current study found no effect of perceptual similarity on normal cognitive ageing. This result illustrated that levels of false alarms between young, old-spaced-repetition and old non-repetition groups were comparable. This appeared to suggest that false alarms in old adults were not driven by general (gist) perceptual information (Koutstaal, Reddy, Jackson, Prince, Cendan, & Schacter, 2003). There was a significant effect of conditions on false alarms. Levels of false alarm for perceptually similar condition were higher than perceptually dissimilar condition. However, there was no reliable interaction between groups and conditions. Overall, these findings appeared to suggest that young as well as old adults mistakenly accepted new words as old words when they were perceptually similar to studied words.