Web portals are Internet-based applications that provide a big amount of data. The data consumer who uses the data given by these applications needs to assess data quality. Due to the relevance of data quality on the Web together with the fact that DQ needs to be assessed within the context in which data are generated, data quality models specific to this context are necessary. In this chapter, we will introduce a model for data quality in Web portals (PDQM). PDQM has been built upon the foundation of three key aspects: (1) a set of Web data quality attributes identified in the literature in this area, (2) data quality expectations of data consumers on the Internet, and (3) the functionalities that a Web portal may offer its users.