In the current investigation, the results of a selection- and a duration-based preference assessment procedure were compared. A Multiple Stimulus With Replacement (MSW) preference assessment [Windsor, J., Piche, L. M., & Locke, P. A. (1994). "Preference testing: A comparison of two presentation methods." "Research in Developmental Disabilities, 15", 439-455] and a variation of a Free-Operant (FO) preference assessment procedure [Roane, H. S., Vollmer, T. R., Ringdahl, J. E., & Marcus, B. A. (1998). "Evaluation of a brief stimulus preference assessment." "Journal of Applied Behavior Analysis, 31", 605-620] were conducted with four participants. A reinforcer assessment was conducted to determine which preference assessment procedure identified the item that produced the highest rates of responding. The items identified as most highly preferred were different across preference assessment procedures for all participants. Results of the reinforcer assessment showed that the MSW identified the item that functioned as the most effective reinforcer for two participants. (Contains 4 figures.)