Research on reading comprehension assessments suggests that they measure overlapping but not identical cognitive skills. In this paper, we examined the potential of eye-tracking as a tool for assessing reading comprehension. We administered three widely-used reading comprehension tests with varying task demands to 79 typical adult readers while monitoring their eye movements. In the York Assessment for Reading Comprehension (YARC), participants were given passages of text to read silently, followed by comprehension questions. In the Gray Oral Reading Test (GORT-5), participants were given passages of text to read aloud, followed by comprehension questions. In the sentence comprehension subtest of the Wide Range Achievement Test (WRAT-4), participants were given sentences with a missing word to read silently, and had to provide the missing word (i.e., a cloze task). Results from linear models predicting comprehension scores from eye-tracking measures yielded different patterns of results between the three tests. Models with eye-tracking measures always explained significantly more variance compared to baseline models with only reading speed, with R-squared 4 times higher for the YARC, 3 times for the GORT, and 1.3 times for the WRAT. Importantly, despite some similarities between the tests, no common good predictor of comprehension could be identified across the tests. Overall, the results suggest that reading comprehension tests do not measure the same cognitive skills to the same extent, and that participants adapted their reading strategies to the tests’ varying task demands. Finally, this study suggests that eye-tracking may provide a useful alternative for measuring reading comprehension.