Hypotheses about possible mechanisms for spillover processes between pro-environmental behaviours are developed and tested by means of structural equation modelling. Data were collected by means of telephone interviews with a representative sample of Danish adults. Personal norms concerning recycling and packaging waste prevention are found to be rooted in the same more general, internalised values. Further, a predicted positive spillover effect from recycling to packaging waste prevention is confirmed. However, whereas a positive spillover effect from recycling to personal norms concerning packaging waste prevention is predicted, the reverse is found. Neither is it confirmed that performing an environmentally friendly behaviour makes attitudinal and more distal antecedents of related behaviours more predictive of the next step in the assumed causal chain.