Objectives: This study investigated word decoding abilities of 1st graders with Developmental dyslexia according to the level of decoding difficulty, meaning availability, word and syllable structure.Methods: Twenty Korean 1st graders with developmental dyslexia participated in 40 word-reading tasks individually. All of them had severe decoding difficulties, even with normal listening comprehension (KORLA; Pae et al., 2015) and intelligence (K-CTONI-2; Park, 2014). The group differences by decoding difficulties were compared considering the meaning of words, the number of syllable-final graphemes, and the position of each grapheme in a syllable.Results: Both the severe and less-severe group in Korean word-decoding difficulties revealed the gaps between word reading and nonword reading. Both groups had decoding difficulties when a word had syllable-final graphemes, while the severe group had even lower performances in word readings with 2 syllable-final graphemes. Both groups showed similar performances in reading syllable-initial graphemes while the severe group had lower performances both in reading syllable-medial vowel graphemes and syllable-final consonant graphemes compared to the less-severe group.Conclusion: Korean 1st graders with developmental dyslexia seemed to be in urgent need of decoding support considering word and syllable structure. Triggering the non-lexical route with non-words considering the grain size of syllable-medial vowel graphemes and syllable-final graphemes would facilitate word decoding abilities of severely dyslexic Korean children.