Aims: Prospective memory (PM: remembering future intentions and activities) is critical to everyday remembering. This study compared a group of never-smokers who reported regular exposure to second-hand smoke (the SHS group) with a group of current smokers (the CS group) and a group of never-smokers who reported never having been exposed to SHS (the non-SHS group) on objective PM. Design: An existing groups design was employed to compare the SHS, CS and non-SHS groups. Participants and setting: Twenty-four SHS, 27 CS and 28 non-SHS were tested on objective PM. All participants were university undergraduates aged between 18–30 years. All participants were tested individually in a laboratory setting. Measurements: The Cambridge Prospective Memory Test (CAMPROMPT) was used to assess objective PM. Age, other drug use, mood and IQ were also measured as covariates in the study. Findings: The non-SHS group recalled significantly more time-based PM tasks than the SHS group (means = 16.3 versus 13.7, P < 0.001) and significantly more than the CS group (CS mean = 11.6, P < 0.001); and the SHS group recalled significantly more time-based tasks than the CS group (P < 0.002). The non-SHS group recalled significantly more event-based PM tasks than the CS group (means = 15.2 versus 11.3, P < 0.002) with no significant difference between the non-SHS group and SHS group (SHS mean = 14.3, P = 0.234); and the SHS group recalled significantly more event-based tasks than the CS group (P < 0.001). Conclusion: Non-smokers exposed to second-hand smoke may suffer impairment in time-based prospective memory.