Introduction: According to Planning Fallacy, people underestimate the time required to complete a task. A review of the social, cognitive, and motivational factors that moderate Planning Fallacy suggests that variability in Web searching tasks would lead to an overestimation of retrieval time, at least when the task duration is short (about 10 minutes). Objective: The goals of this pilot study are twofold: to check the accuracy of forecasts when users estimate the time required to retrieve information on the Web, and to understand users' strategies for dealing with the Web for multipurpose documentation. Method: Participants (n = 32) were asked how long it would take to answer four encyclopedic questions on the Web; questions were in various fields with two levels of difficulty and two types of answers (qualitative vs quantitative). We compared estimations of the time required to retrieve specific information on the Web with the actual retrieval time. Forecasts were made before and after the effective retrieval task (within-subjects design). Results: A significant and large overestimation of the anticipated time was observed, especially for questions with a qualitative answer. The overestimation range was between 195% and 473% for mean search durations between 4.5 and 10.3 min. Task perceived difficulty was the best predictor of time anticipation (r 2 textless 0.32). Web search self-efficacy and experience contributed slightly to the overestimation but only for easy questions. Conclusion: Overestimation of the time required to complete a Web searching task (i.e. pessimistic Planning Fallacy) results from a combination of factors: short length of tasks, variability in task difficulty, and the qualitative or quantitative nature of the correct answer. Search time forecast could be used as a benchmark to improve Web usability. ?? 2012 Elsevier Masson SAS.