Causes of abnormal (from the viewpoint of traditional views on the cis labilization effect) enhancement of the tendency of pentacarbonyltechnetium halides to decarbonylation in the series I–Br–Cl–F are discussed. Two possible causes are considered: “nonclassical” halogen···cis-C interaction and electrostatic interactions of the halide ligand with the Tc atom in the initial complex and pentacoordinate transition state. Relative stabilization of the transition state due to electrostatic interactions is concluded to be the most probable cause of the observed trend.