Results of investigation of processes in waveguide pulsed gas lasers on atomic and molecular transitions are presented. Conditions of population inversion forming in N2(337 nm), XeCl, and Ne-H2(585 nm) lasers excited by longitudinal and barrier discharges in thin cells with various diameters were investigated. In the thin capillaries, significant changes of discharge forming conditions due to variation of Paschen’s curve have been observed. Particularly, in the capillaries with diameter less than 120 μm, optimal conditions of electronic temperature for the excitation of nitrogen laser at the self-breakdown have been achieved. We obtained the generation and investigated dependencies of an output power on gas pressure in the self-breakdown nitrogen laser. We studied the efficiency of XeCl excimer molecules formation in the plasma of the barrier discharge. Conditions required for efficient formation of excimer molecules in the plasma of barrier discharge was found. By double pulse technique the amplitude-frequency characteristics of efficiency of XeCl excimer molecules formation in the plasma of the barrier discharge were tested. Up to the frequency 30 kHz, there was no significant decrease of second pulse amplitude. We studied the dependence of efficiency of luminescence at the transition 3p’[1/2]0-3s’[1/2]0 of Ne (585,3 nm) on the gas pressure and the charging voltage of storage capacitors in pure Ne or with H2 additions in following ratios Ne:H2 (3:1, 2:1) with excitation by longitudinal discharge in narrow capillary 500 μm. The saturation of luminescence intensity occurs at the high pressure was found. The decreasing of luminescence at the additions of hydrogen was observed.