Floristic diversity of woodless gaps and openings has been studied within krummholz stands of Pinus mugo on the summit plateau of the eastern Giant Mts., the Sudetes. Particular open sites have been outlined from available orthophotomaps, and effects of their size analysed by means of a species-area model, calculated for both woodless openings and open grassy tundra. According to the regressions, decrease of the species number in relation to diminishing sample plots is steeper in the openings (z = 0.151) than in mat-grassland (z=0.118); openings smaller than 70 m2 contain less than 90 % species of the open grasslands. Non-clonal herbs are more frequent in openings larger than 100 m2 in size. Species composition and abundance in gaps and openings have been analysed by means of ordination (DCA, CCA) and classification (TWINSPAN) techniques. Three categories of open sites were identified: (i) Sites smaller than 2 m2, recognized as gaps, do not contain grassland species and regularly serve for establishment of young krummholz specimens. (ii) Openings surrounded by taller krummholz display a cyclic succession between krummholz and grassland, which is expressed by the presence of floristic elements typical for the Myrtillo-Pinetum mughi community. (iii) Openings marked by continual occurrence of species of the Carici fyllae-Nardetum community, and by higher frequency of cryogenic patterned grounds. Spatial patterning of the three above-mentioned categories in the entire study area suggests a differentiation of three types of krummholz-grassland ecotones: (1) hygric type with very large openings up to 20002500 m2 and well-developed cryogenic patterned grounds, (2) eolic type with equal share of krummholz and grassland, and with 5 % openings between 100 and 1400 m2 in size, and (3) mesic type with frequent krummholz regeneration and less prominent cryogenic patterned ground, where closed-canopy krummholz prevails above the openings smaller than 500 m2 in size. Management of human-introduced plantations of krummholz, with regard to their density, should be performed in accordance to environmental differentiation of the above-mentioned natural ecotones.