This paper reports two studies that investigate differences in comprehension monitoring skills between good and poor comprehenders. Two groups of 9- to 10-year-olds, who were matched for reading vocabulary and word recognition skills but who differed in comprehension skill, were selected. In the first study, in which the children were required to find anomalous words and phrases, the skilled comprehenders engaged in more accurate monitoring of sentence level anomalies (but not word level anomalies) than did the poorer comprehenders. In the second study, the comprehension monitoring task required the children to detect pairs of sentences, in short texts, that were contradictory. In addition, the working memory demands of the task were varied by placing the two items of inconsistent information either in adjacent sentences, or in sentences that were separated in the text by several others. As in the first study, less-skilled comprehenders performed more poorly on the detection task, but the difference between the groups was considerably more pronounced when the sentences were separated than when they were adjacent. In addition, the children were given a numerical working memory test, and the poorer comprehenders performed more poorly on this test. However, although working memory performance was related to performance on some of the error detection tasks, comprehension ability was also a good, and sometimes better, predictor. The results are discussed in terms of the different cognitive abilities that might contribute to efficient comprehension monitoring.