Since the year 2000, Portugal has participated in the PISA – Programme for International Student Assessment. The performance of the Portuguese students in reading literacy exhibit little change in the three cycles of PISA. However, behind these apparent stability it is important to determine whether the performance of the students maintains the same profile, in terms of reaching the same levels in different types of continuous texts (narration, exposition, description, argumentation, instruction) and non-continuous texts (tables, diagrams, maps, forms, calls and advertisements, vouchers, certificates). To do so a deep analysis of the 2000, 2003, and 2006 databases – in what concerns the test results – will be performed in order to determine the performance levels in each PISA cycle and regarding the same type of text. From the conjugation of these results with the data gathered from the student questionnaires, it is possible to find out the linking between item performance and characteristics of the students. Methodology or data analysis methods: The two data types will be utilized: test results together and student questionnaires. A multivariate analysis will be performed in order to identify the relationship between student performance and the mentioned factors. Conclusions: Explaining the evolution of the Portuguese student performance in reading literacy – which factors influence results.