The iodonium ion-mediated ring expansion of olefinic cyclobutanols 20, 21, and 25 gave mixtures of iodoalkylated cyclopentanones 33a-c and 34a-c. On the other hand, the same reaction of 29, 30, and 32 stereoselectively afforded iodoalkylated cyclopentanones 33d and 33e. The stereochemical course of this reaction is also discussed.