Background: Obesity campaign evaluations have used campaign awareness to assess impact, yet have not compared unprompted campaign recallers, with prompted recallers and those with no campaign recall. Using data from an Australian mass-media obesity prevention campaign linking waist circumference and chronic disease we examined whether those with different degrees of campaign recall are distinct groups demographically and for subsequent campaign effects. Methods: A national cross-sectional telephone survey of randomly selected adults aged 18 to 65 years was conducted post-campaign (n = 2812) covering campaign recall, self-reported diet and physical activity (PA) and waist-measuring knowledge, behaviours and intentions to make lifestyle changes. Respondents were divided into three groups indicating campaign recall: Unprompted Recallers (n=1154); Prompted Recallers (n=1284); and No Recallers (n=374) and compared on demographic, knowledge, and behavioural risk factors for obesity/chronic disease. Results: Unprompted Recallers were more likely to speak English at home (p<.001), be in the primary campaign target group (25-45 years with children) (p<0.001) than the other two groups and to be university educated and female than the Prompted Recall group only (p=0.001). Unprompted Recallers had better knowledge about recommended waist circumference (p<.001), fruit (p=0.004), vegetable (p<0.001) and PA guidelines (p<0.001) than both the other groups. The No Recall group was less likely than the other two to be overweight/obese (46% vs 55%, p=0.020 and 54%, p=0.037), comparable on meeting fruit consumption and PA guidelines but more likely to meet vegetable intake recommendations (than Unprompted Recallers only). Conclusions: Unprompted recallers were more knowledgeable about campaign messages; behaviour change and intentions to change were stronger for the two recall groups compared with the No Recall group but not different between them. The current analysis revealed subtle differences in campaign exposure and/or attendance by different demographic subgroups that would not be apparent in a simple aware/unaware dichotomy.