Information and communication technologies (ICT), namely the Internet, can play a valuable educational role in several school subjects, including science education. The same applies to problem-based learning (PBL), that is, a student-centered active learning methodology that can prepare students for lifelong learning. WebQuests (WQs) combine PBL and Internet use, and they can reduce the probability of having students surfing the Internet without any clear purpose. The objective of this paper is to investigate to what extent WQs available from Portuguese schools' and universities' websites, focusing on the "Sustainability on Earth" eighth-grade school science theme, are consistent with a PBL perspective. Results from content analysis of 92 WQs indicate that the WQs selected for this paper are rarely consistent with PBL requirements. Teachers should be both aware of this issue and ready to improve the WQs available before using them in their science classes so that greater educational advantage can be generated from this powerful tool.