∗+ & Tubular diffusion flames are compared with opposed jet diffusion flames numerically to show the effect of curvature on diffusion flames. The numerical results show that, as in premixed flames, positive curvature strengthens the preferential diffusion and negative curvature weakens the preferential diffusion; the strengthening or weakening effect is proportional to the ratio of flame thickness to flame radius. Since the flame temperature is related to the preferential diffusion, flame curvature affects flame temperature and extinction stretch rate. Since the flame thickness is related to pressure, the curvature effects also depend on pressure. H2/N2–air and CH4/N2–air diffusion flames with different flame radii and pressures are presented to verify the analysis.