The performance of Portuguese students in reading literacy exhibits little change in three PISA cycles (2000, 2003, 2006). Despite this apparent stability it is important to determine whether the performance of students maintains the same profile, in terms of reaching the same levels in different tasks, text formats, and reading situations. To do so, test results in each cycle will be analyzed to determine the performance levels in view of the same characteristics of a text – reading task, format and reading situation. This analysis of reading achievement provides information on the students’ levels of performance and their evolution throughout the years. It also allows to identify the main difficulties the students encounter when performing reading comprehension tasks. Yet, this analysis does not provide detailed knowledge of students’ perceptions regarding the type of tasks and the difficulty level associated to these tasks, neither about the degree of familiarity of students with different texts and tasks. We therefore conducted an exploratory study by giving the PISA test to a small number of students (classes) in school years 9 and 10 (typically 15-year olds). We will present the main conclusions drawn from this study, and a critical analysis of the students’ outcomes.