The purpose of this study was to classify Korean readers into subgroups based on their reading achievement and to examine the relationships between these subgroups and a set of cognitive-linguistic variables. The reading achievement and cognitive-linguistic skills of 394 elementary school students were measured and the data were analyzed by disaggregating into primary grade level (i.e., Grades 1-3) and intermediate grade level (i.e., Grades 4-6). The main results are summarized as follows. First, three subgroups of readers were found based on the reading achievement for the primary grade level: "very poor word readers and poor comprehenders," "poor readers," and "average readers." Second, four subgroups of readers were found based on the reading achievement for the intermediate grade level: "very significantly poor readers," "very poor readers," "average word readers but poor comprehenders," and "average readers." Third, vocabulary, rapid naming, phonological memory, and phonological awareness were cognitive-linguistic variables that significantly differentiated "very poor readers" and "poor readers" from "average readers" for the primary grade level. Fourth, phonological memory, rapid naming, sentence repetition, and listening comprehension were cognitive-linguistic variables that significantly differentiated "very poor readers" and "poor readers" from "average readers" for the intermediate grade level. This article also discusses the limits of this research and the implications in practice. Finally, this article touches upon the direction of future studies.