This study examined the preparations carried out to establish indoor garden areas in Seoul metropolitan subway stations and in 5 other metropolitan cities subway stations in order to present findings on how these preparations might be improved. The preparation ratio for indoor garden areas among Seoul metropolitan subway stations was 6.9%, 38 places, and the ratio overall for 5 metropolitan cities was 21.6%, 54 places. Among the 5 metropolitan cities, the ratio was 26.7% in Busan metropolitan city, 20.0% in Gwangju metropolitan city, 11.6% in Daegu metropolitan city, 18.2% in Daejeon metropolitan city, and 10.3% in Incheon metropolitan city. With regard to the results comparing the decoration ratio with natural flowers and artificial flowers among the prepared stations with indoor gardens, in the case of Seoul metropolitan area, places decorated with natural flowers numbered 23, and the ratio was 60.5%, but, in case of the 5 metropolitan cities, places decorated with natural flowers numbered just 6, and the ratio was just 11.1%. In the case of garden ornaments as material introduced in Seoul metropolitan area subway stations decorated with natural flowers and the 5 metropolitan cities subway stations, one to three kinds of ornament were introduced per each place, and the ornament items included rocks, garden lanterns, ponds, stone mortars, stone lamps, fountains, sculptures, mini water mills, and windmills. The introduced trees at subway stations in Korea that were decorated with natural flowers included 93 species of 70 genera of 45 families. The introduced trees included 87 species of 67 genera of 42 families in Seoul metropolitan area subway stations, and the introduced trees included 28 species of 16 genera of 11 families in the 5 metropolitan cities subway stations. Native trees included 21 species of 20 genera of 17 families. As for scenery formation elements according to the height of trees, in the case of Seoul metropolitan area, the introduced trees included 22 species of upper trees, 15 species of middle trees, and 46 species of lower trees. In the case of the 5 metropolitan cities, the introduced trees included 1 species of upper trees, 5 species of middle trees, and 18 species of lower trees. Therefore, volume and visual diversity in Seoul metropolitan area was provided by the height and bulk of trees, but the volume of scenery and diversity in the 5 metropolitan cities was insufficient. In the case of Seoul metropolitan area, using indoor garden spaces is necessary to connect with mini libraries, resting spaces, and snack bars, and various using types are necessary. In the case of the 5 metropolitan cities, only the visual image was provided, and therefore an activation plan for using spaces is necessary.