In our work we develop the computer analysis of the CPT-dip properties. We investigate the dependencies of CPT-dip width, depth and contrast on the radiation fields intensities and detunings, the magnetic fields strength, and the relaxation constants. CPT is observed in the population dynamics of two real three-level atomic systems. One of them is a (Lambda) - type system composed of the magnetic sublevels of 6P1/2, 6P3/2 and 7S1/2 states of Tl atom, the other one is a (Xi) -type system of the magnetic sublevels of 3S1/2, 3P3/2, 5S1/2 states of Na atom. The systems interact with two monochromatic laser fields and magnetic field, which is perpendicular to the laser propagation direction for the lambda-system and parallel for the (Xi) -system. On both cases polarization and mutual configurations of the fields are chosen specific, so that one can select the isolated three- level subsystems in multilevel atomic systems. We observe that the obtained dependencies are different from those in reference 1. It may be explained with non-equal Rabi frequencies and decay rates of neighboring transitions, which are the characteristic feature of real atoms.