This study investigated the effect of language experience on the categorical perception of Cantonese vowel duration distinction. By comparing Cantonese and Mandarin listeners' performances, we found that: (1) duration change elicited categorical perception in the performance of Cantonese listeners, but not in Mandarin listeners; (2) Cantonese listeners were affected by the vowel quality differences, whereas Mandarin subjects were generally unbiased towards the quality differences; (3) effect of duration was overridden by the vowel quality [a] condition in the performance of Cantonese listeners. Our findings suggested that vowel quality is incorporated as a phonological cue in Cantonese.