Swimlane diagrams are regarded to be an important tool when validating business rules and procedures with stakeholders because they are believed to convey information about business process models effectively and efficiently. However, the literature lacks empirical support for such an assumption; the literature is void of studies evaluating the efficacy of swimlane diagrams. We conducted two studies that required students to examine swimlane and non-swimlane diagrams of the same business process. Based on 142 and 131 responses, respectively, for the two studies, we found that the non-swimlane diagrams are more effective overall in conveying information to stakeholders, but that swimlane diagrams are more efficient in conveying information to stakeholders, especially when they include important visual clues and handshake activities.