In a normal and an abnormal ELCAD plasmas the density of electrons and positive ions were estimated from the earlier measured values of the cathodic current density, the cathode fall, the electric field, the length of cathode dark space, the kinetic energy, the last free path of positive ions hitting the cathode and the rate of secondary electron emission. In a normal ELCAD, the density of positive ions forming the space charge: $n_{sp}^{+}$ ≈ 5.7×1012 cm-3, the density of positive ions hitting the cathode: n + ≈ 1.1×1012 cm-3, the electron density at the cathode: $n_{e,c}$ ≈ 3.7×1011 cm-3, the electron density at the end of cathode dark space: n e ≈ 5.7×1012 cm-3 and the multiplication of electron in cathode dark space M ≈ 15.3 were obtained. In an abnormal case, $n_{sp}^{+}$ ≈ 2.1×1013 cm-3, n + ≈ 4.3×1012 cm-3, $ n_{e,c}$ ≈ 3.9×1012 cm-3, n e ≈ 2×1013 cm-3, M ≈ 5.17 were received.