Behavioral economic demand for cannabis (i.e., relative reinforcing value) can be measured via marijuana purchase tasks (MPTs). However, commodity ambiguities pose challenges and design concerns exist regarding current MPTs. The aim of this 2-phase study was to modify and improve a MPT using qualitative methods. Phase I: Focus groups were conducted with regular (i.e., average use ≥ once/week) cannabis users (n = 31; 6-7 per group M[SD] age = 26 [7]; 28% female). Focus groups followed a semistructured agenda, and executive summaries were made concerning key MPT themes. Feedback was used to refine the MPT. Phase II: Cognitive interviews using the refined MPT were conducted with regular cannabis users (n = 20; M[SD] age = 28 [8]; 50% female). Phase I: Focus group analyses highlighted 4 critical areas for MPT improvement: (a) unit of purchase, (b) cannabis quality, (c) time duration specified for use episode, and (d) price. Participants suggested using grams as the unit of purchase, tailoring cannabis quality to the individual, and clarifying intended episode length. Phase II: Cognitive interviewing indicated additional areas for task refinement, resulting in a second iteration of the MPT based on the 2 phases. Qualitative research in both phases suggested a number of substantive modifications to the MPT format. MPT modifications are expected to improve comprehension, ecological validity, and general construct validity. Findings highlight the importance of careful instructional set development for drug purchase tasks for heterogeneous products that do not have standard units of consumption. (PsycInfo Database Record (c) 2021 APA, all rights reserved).