Writing is probably the most difficult skill to acquire for most learners of English. The goal of this paper is to find typical problems of English writing by Korean learners through the comparison with English native speakers' writing. The participants were 23 Korean university students at the Seoul National University of Education and 23 American university students at West Chester University of Pennsylvania. They were asked to write a description of three pictures which were connected in a series. Although it limited the range of vocabulary and writer's thoughts, the picture description was expected to produce some common results to compare among the participant's writings. It was found that there was a huge difference between the two groups of participants not only in lexis and syntax but also in writing styles and supporting details. First, Korean participants used standardized phrases such as it rains and one rainy day much more often than American Participants. Interestingly, five Korean participants wrote it rains cats and dogs, whereas only one American participant used that expression. One the other hand, the expression, a gust of wind was used by most American participants, but no Korean participants used it. These differences showed many important teaching implications to the teaching of English writing. To be better English writers, it is necessary for Korean students to be directly exposed to English writing patterns and conventions as well as to improve their linguistic competence such as English lexis and syntax.