The experimental results on study of characteristics of the high-pressure volume (diffuse) discharges in nitrogen at applying to the interelectrode gap voltage pulse with the amplitude of hundreds kV, duration of several ns and the rise-time of fraction ns are presented. At the pressure range of nitrogen in (0.2-4)×105 Pa, the discharge transformation from the diffuse form to the spark is investigated. Dependencies of the current amplitude and FWHM of the runaway electron beam current on nitrogen pressure are determined. It is shown that the generation of the Supershort Avalanche Electron Beam (SAEB) leading to the formation of diffuse discharge in the gap has a significant influence on the development of the discharge. At the pressures indicated above, the dependence of the time delay of SAEB’s moment generating relatively discharge current beginning on pressure are obtained. According to this dependence, the time delay changes as pressure increases and it is minimal at pressure of 2×105 Pa. Also, it is shown that the maximum peak value of diffuse discharge current pulse decreases with increasing pressure. At a pressure of 0.5×105 Pa with the use of blade electrodes and the N2∶SF6=10∶1 active medium of length 6 cm, the output laser energy of 2 mJ is achieved for the pulse power of 0.55 MW. It is reported that during the treatment of the AlBe foil by the Runaway Electron Preionized(REP) discharge in atmospheric pressure air, its surface layer is cleaned from carbon, and atoms of oxygen penetrate into the foil (by 450 nm per 300 pulses).