Аннотация:We present theoretical UBVI- and bolometric light curves of SNe Ia for several explosion models, computed with our multi-group radiation hydro code. We employ our new corrected treatment for line opacity in the expanding medium. The results are compared with observed light curves. Our goal is to find the most viable thermonuclear SN model that gives good fits not only to a typical SN Ia light curve, but also to X-ray observations of young SNIa remnants. It appears that classical 1D SNIa models, such as deflagration W7 and detonation DD4, fit the light curves not so well as a new 3D deflagration model by Reinecke et al (which is averaged over angles for our LC modelling). This model seems good also in reproducing X-ray observations of Tycho SNR. We believe that the main feature of this model which allows us to get correct radiation during the first month, as well as after a few hundred years, when an SNR forms, is a strong mixing that pushes material enriched in iron and nickel to the outermost layers of SN ejecta.