*both* the photometric *and* spectroscopic observations into account to obtain an adequate hydrodynamic model (Utrobin [@utr05]). Now such an approach should be applied to SN 1999em.

Here we present the comprehensive hydrodynamic study of SN 1999em complemented by the atmosphere model with the time-dependent kinetics and energy balance. A brief description of the hydrodynamic model and the atmosphere model based on it is given in Sect. \[sec:snmodel\]. The study of SN 1999em we begin with a construction of the optimal hydrodynamic model (Sect. \[sec:optmod\]). Then we continue with a question: at what distance to SN 1999em, short or long, the hydrodynamic model and the proper atmosphere model are consistent with the photometric and H$\alpha$ line observations (Sect. \[sec:evidis\]). The time development of the optimal hydrodynamic model is presented in Sect. \[sec:devmod\], and its general regularities in Sect. \[sec:genpro\]. The basic relationships between the physical and observed parameters for SNe IIP similar to the SN 1999em event are obtained in Sect. \[sec:phyobs\], while in Sect. \[sec:sn87a\] we address the comparison of SN 1999em with SN 1987A. In Sect. \[sec:disc\] we discuss our results from the theoretical and observational points of view. Finally in Sect. \[sec:concl\] we summarize the results obtained.

We 