Charge trapping in the insulator of a metal‐oxide‐semiconductor (MOS) structure strongly influences photocurrents resulting from electron photoinjection from the gate, or from the semiconductor electrode, into this insulator. This influence may be used to determine trapped charge distributions (profiles) in the dielectric layers of MOS structures. In this paper, several trapped charge profiles are considered, and the influence of these charges on the MOS structure photoelectric characteristics is discussed. Detailed solutions are derived for uniform, step, delta, rectangular, exponential, and Gaussian distributions of electrons trapped in the dielectric of a MOS structure. All these solutions are based on the barrier position mode approximation of the Powell–Berglund formulas. A comparison of experimentally obtained photocurrent‐voltage characteristics of a MOS structure (taken both before and after the charge trapping took place) with characteristics calculated using expressions derived in this paper allows approximate determination of the trapped charge profile in this particular sample.