Ground ozone levels (O₃, 0 ~ 11 km) have significantly increased over the past decades and an increase of O₃ concentration has been predicted for future. Moreover, the anthropogenic nitrogen deposition has been increasing in Northern hemisphere. Especially in Asia, negative effects of O₃ and (NH₄)₂SO₄ deposition on forest ecosystem have been concerned. Previous studies have reported negative effects of elevated O₃ on Japanese larch (Larix kaempferi) was moderated by NH₄NO₃ loading. However, the mechanism of this response is not still revealed, and further, the response of hybrid larch F₁ (L. gmelinii var. japonica x L. kaempferi) is unknown. We examined combined effects of elevated O₃ and (NH₄)₂SO₄ on the growth of both larch seedlings during two growing seasons. At leaf scale, species difference in the stomatal responses to interactive effects was observed. Especially, physiological activities of hybrid larch F₁ will be inhibited more than Japanese larch. At individual level, the leaf whole dry mass ratio (LWR) of hybrid larch F₁ was lower than Japanese larch under (NH₄)₂SO₄ loading. This tendency of LWR was also observed in interactive effects but not significantly. Based on these results, we may conclude the O₃ sensitivity of hybrid larch F₁ will be increased by (NH₄)₂SO₄ deposition.