This research contributes to theory in three ways. Firstly, novel sources of heterogeneity are investigated to assess their effectiveness in identifying subgroups within the market which are homogeneous in their volunteering behaviour. Secondly, the assumption that general volunteering behaviour is indicative of volunteering for specific organisations is challenged. Thirdly, the Theory of Planned Behaviour is expanded to account for heterogeneity, and an additional construct added to improve the predictive ability of the model. Results provide insight into ways of segmenting the volunteer market to identify groups which are homogeneous in their attitudes and volunteering behaviour. This allows managers to (1) identify the generic image position which is most preferred for their organisation; (2) understand which people are most likely to volunteer for their organisation; and (3) understand how to reach these people and which messages to use. Ultimately, this information enables more efficient spend of the limited marketing dollars available, and maximises the number of volunteers recruited and retained by volunteering organisations.