The x‐irradiation of a single crystal of Ph₃SeCl produces the formation of a radical showing hyperfine interaction with ³⁵Cl and ⁷⁷Se. The ESR tensors are determinated: g₁=1.998, g₂ =2.029, g₃=2.052, T₁(³⁵Cl) =138 MHz, T₂(³⁵Cl) =30 MHz, T₃(³⁵Cl) =27 MHz and T₁(⁷⁷Se) =987 MHz, T₂(⁷⁷Se) =132 MHz, T₃(⁷⁷Se) =29 MHz. The angles between the g₁, T₁(³⁵Cl) and T₁(⁷⁷Se) directions are less than 9°. The sign assignments corresponding to a total spin density close to unity lead to the following spin populations: c²_p (Cl) =0.26, c²_p (Se) =0.80. The radical is identified as being Ph₂SėCl and is compared with its homologous Me₂ṠBr.