Background: A number of studies report that few questions are asked in classrooms and that many of them are shallow questions. Aims: This study investigates the way in which reading goals determine questioning on scientific texts. Reading goals were manipulated through two different tasks: reading for understanding versus reading to solve a problem. Sample: A total of 183 university students. Methods: In the first and third questioning experiments the participants read two short texts. Students in one condition were instructed to understand the texts, while in the alternative condition they had to read texts to solve a problem. Students were instructed to write down any questions they might have about the texts. The questions were categorized according to the type of underlying obstacle: associative, explanatory or predictive. The second experiment used a think-aloud methodology to identify the mental representations generated by the students. Results and Conclusions: The two questioning experiments show that the questions asked depend on the reading goals. Significantly more explanation questions were asked in the understanding condition than in the problem-solving condition. Also, the two conditions were found to have a different influence on the generation of association and explanation questions. Very few prediction questions were asked in either condition. The think-aloud experiment revealed that the mental representations attempted by readers under the two conditions were indeed different. In conclusion, the experiments showed that, given a certain textual input, readers" questions depend on the reading goals associated with tasks.