This paper examines how economic theory can inform qualitative analysis and what an evaluator should consider when incorporating an economic theory. The study applies a specific economic theory, the theory of rational addiction, to a series of interviews with tobacco users before and after a cigarette tax increase. This study tests the extent to which the economic theory added value to the analysis of qualitative data and the implications this has for an evaluation. The researcher first analyzed the interviews using codes created from the content of the transcripts; she then analyzed the interviews again using predetermined codes from the theory of rational addiction. The study found that using this economic theory provided another lens through which the evaluator could interpret the data. In addition to revealing extra themes, the theory also helped the researcher better understand her positionality and assumptions about the participants.