To enhance the effectiveness of online comparisons from a manufacturer's point of view, we develop a framework for the comparison challenge approach. To develop the comparison challenge framework, we analyze 12 factors that determine the characteristics of comparison and propose models of valuable comparison challenges using the CompareMe and CompareThem strategies. We demonstrate the approaches with the example of PC selection. To help plan the comparison challenges, we formulate a mathematical programming model that maximizes the total value of comparison under the constraints of comparison opportunity and budgetary limitation. The model is applied to eight comparison scenarios, and its performance is contrasted with the view of balancing long-term perspective and short-term revenue increase. The performance of the comparison challenge approach is contrasted with those of random banner and similarity-based comparison approaches, and shows a substantially higher effect. (C) 2006 Elsevier B. V. All rights reserved.