In line with the studies in EFL/ESL contexts confirming the positive relationship between critical thinking ability and reading comprehension, this study intended to investigate how frequently critical thinking was used in the questions of EFL reading comprehension in Iranian high school books. To this end, Critical Reading Questions (CRQs), Vocabulary in Context (VIC), Literal Comprehension (LC), and Extended Reasoning (ER) were identified. The focus of the study was on ER questions, which lead to critical thinking. The reason was that the crucial problem of the students lies in textually implicit information in the texts. To classify the questions for CRQs, Petersonʼs (2008) model was employed, and to specify critical thinking question types, a framework proposed by Academic Skills Unit (2008) was used as reference. To collect the data, the researchers identified the total percentages and frequencies of questions related to the passages in English Books I, II, III, and Pre-University. The findings revealed very little attention to critical thinking within the objectives of the questions of Books I, II, and III. Fortunately, the Pre-University book could be helpful to provide the students with fruitful exercises which fostered the application of ER questions. This study highlights the need for raising researchers' and teachersʼ awareness of ER-based reading comprehension questions. Manuscript profile