The main physical principles of temperature field simulation in homogeneous and discrete structures are considered. A numerical modeling of temperature fields in the real low-voltage display with various physical properties of the phosphor screen is presented. The continuous layer model was applied to calculate the average temperatures and temperature gradients in the phosphor layer. Calculations in terms of the orthogonal cell model were performed to estimate the average temperature distribution and temperature gradients in separate parts of the luminescent layer. The temperature difference between the upper and lower surfaces of the phosphor screen is insignificant, not exceeding 20 K at an applied power density of 1 W/cm(2). At the same time, their absolute temperatures reach as much as 500 K. The temperature gradients on the grain contacts are as high as 10(8) K/m while their mean values given by the homogeneous structure model did not exceed 2 x 10(6) K/m.