Working memory predicts children's reading comprehension but it is not clear whether this relation is due to a modality-specific or general working memory. This study, which investigated the relations between children's reading skills and working memory (WM) abilities in 3 modalities, extends previous work by including measures of both reading comprehension and reading accuracy. Tests of word reading accuracy and reading comprehension, and working memory tests in three different modalities (verbal, numerical and spatial), were given to 197 6- to 11-year old children. The results support the view that working memory tasks that require the processing and recall of symbolic information (words and numbers) are better predictors of reading comprehension than tasks that require visuo-spatial storage and processing. The different measures of verbal and numerical working memory were not equally good predictors of reading comprehension, but their predictive power depended on neither the word vs. numerical contrast nor the complexity of the processing component. In general, performance on the verbal and numerical working memory tasks predicted reading comprehension, but not reading accuracy, and spatial WM did not predict either. The patterns of relations between the measures of working memory and reading comprehension ability were relatively constant across the age group tested.