This paper investigates the nature of stated preferences for reducing air pollution impacts. Specifically a contingent valuation (CV) experiment is designed to elicit individuals’ values for reducing these impacts and to examine how these may change when multiple schemes for reducing differing impacts are valued. The novel survey design allows simultaneous testing for the presence of several anomalies reported in the CV literature within the same context, including (i) scope sensitivity (ii) part-whole or substitution effects (iii) ordering effects and (iv) visible choice set effects. Results indicate some scope sensitivity and interaction between ordering effects and visible choice set effects, as well as substantial part-whole or substitution effects between two exclusive schemes. A practical consequence of these findings is that estimates of the value of combined programmes may not readily be obtained by summing the values of their constituent parts obtained using the CV method.