He wrote a lot of poetry. He started as a poet. His book, "The Incognito Lounge," made quite a splash in the poetry scene long ago. I was taken with it myself.
Here are some links to Denis Johnson's poems, which are a big influence on many of my contemporaries (poets in their 20s during the 1980s). It was through David St. John that I and other '80s-era Johns Hopkins Writing Seminars grad students discovered Johnson's darkly illuminating voice. I always hoped he'd return to poetry at some point in the future.