The purpose of this study was to investigate the effects of text difficulty and reading comprehension ability on English summary writing of Korean EFL readers. Forty-four university freshmen participated in this study, in which they were asked to read two expository English texts and write a summary in English for each source text. Their summaries were analyzed in terms of the content idea units, idea units at different importance levels, accuracy, paraphrase and integration, and intrusion. The results showed that higher-level readers were able to identify the important information and overall content ideas of the source text better than lower-level ones. The more proficient readers were also more skillful at integrating the ideas of the original text and reproducing them in their own words than the less proficient readers. Moreover, regardless of the reading comprehension level, there were less inaccurate statements in the easier text summarization in both groups. The pedagogical implications of these findings are discussed.