This study was aimed to investigate the genre identify of children's poems through the issue of designating the boundaries of genre between ‘the poems for children’ and ‘the poems for adults.’ Specifically, the study examined the issues of Yun Dong-joo's writing and the cases of genre classification for his works, in terms of ‘creation,’ ‘publication’ and ‘research and criticism discourse.’ Yun Dong-joo was one of the most representative authors that were actively involved in writing both children's poems and ordinary poems. He clearly recognized the differences in writing between these two types of genre and made sincere efforts to put them into practice. However, he was not able to publish his book of poems during his lifetime. Therefore, the issue of genre classification in his books of poems published posthumously could only be determined by the interpretations and judgment of publishers or literary researchers. So far, it has been known that there were circa 30 to 40 children's poems written by him, but there were only 17 that were assumed to be written by him as children's poems through the objective indices. Accordingly, there were several texts of his works located in the boundaries of genre so that it would be difficult to clearly classify their genre. Indeed, such texts provided us with an opportunity to fundamentally reconsider what the criteria of 'true children's poems’and ‘true ordinary poems’ would be and what influences such criteria would have.