<p>Diversity and regeneration of woody species were investigated in two ecological niches <i>viz.</i> gap and intact vegetation in old-growth seasonally dry <i>Shorea robusta</i> forests in Nepal. We also related varieties of diversity measures and regeneration attributes to gap characteristics. Stem density of tree and shrub components is higher in the gap than in the intact vegetation. Seedling densities of <i>S. robusta</i> and <i>Terminalia alata</i> [<i>T. elliptica</i>] are higher in the gap than in the intact vegetation, while contrary result is observed for <i>T. bellirica</i> and <i>Syzygium cuminii</i> in term of seedling density. The complement of Simpson index, Evenness index, and species-individual ratio in the seedling layer are lower in the gap than the intact vegetation. Gap size can explain species richness and species establishment rate. Gaps created by multiple tree falls in different years have higher seedling density of <i>S. robusta</i> than gaps created by single and/or multiple tree falls in the same year. In conclusion, gaps maintain species diversity by increasing seedling density, and favour regeneration of Sal forests. In addition to gap size, other gap attributes also affect species diversity and regeneration.</p>