This study examines how passage availability and reading comprehension question format (open-ended vs. multiple-choice) influence question answering. In two experiments, college undergraduates read an expository passage and answered open-ended and multiple-choice versions of text-based, local, and global bridging inference questions. Half the participants were allowed to refer to the passage when answering the questions and half were not. Participants' prior domain knowledge relating to the text contents was assessed using multiple-choice and open-ended questions. Correlation-based analyses in the two experiments indicated: (a) a decline in the relationship between prior domain knowledge and comprehension when the passage was available during question answering; and (b) a high correlation between multiple-choice and open-ended question answering performance when the passage was not available for reference. Overall the results indicate that the nature of the reading comprehension assessment is influenced by the specific task with which comprehension is assessed. (Contains 1 figure and 6 tables.)