Effective atomic numbers were measured for InSe and InSe having different Holmium concentrations measured in the energy region 15.746-40.930 keV using a Si(Li) detector. InSe:Holmium(0.0025), InSe:Holmium(0.0050), InSe:Holmiurn(0.025) InSe:Holmium(0.05) and InSe crystals have been grown by the Bridgman-Stocbarger method. The measured values were compared with the theoretical ones obtained using WinXConn being a Windows version of XCOM on the basis of mixture rule. The objective of this work is to show that there is a relation between effective atomic numbers and doped Ho fractions to InSe. (C) 2009 Elsevier B.V. All rights reserved.