Presented in this article are considerations regarding modeling of flow boiling in conventional, small-diameter channels and minichannels. A concise survey of available methods for prediction of heat transfer coefficient in saturated boiling regime is given and in that light a modified author's own model is presented. The presented model, contrary to other approaches, finds application in the cases of both conventional and small-diameter channels. The results of calculations are compared with some experimental data available from literature on conventional-size tubes and also minichannels. Obtained agreement is satisfactory.