A systematic study of the doping of the Mn sites by various elements (Mg 2 + , Fe 3 + , Al 3 + , Sn 4 + , Ti 4 + ) in three charge ordered manganites - La 0 . 5 Sr 1 . 5 MnO 4 , LaSr 2 Mn 2 O 7 and Pr 0 . 5 Ca 0 . 5 MnO 3 - has been performed. An abrupt disappearance of the charge ordered state is observed, for low level of dopant (∼1-2%) whatever its nature. The change of slope associated to the charge ordering on resistivity curves as well as the coupled antiferromagnetic transition on susceptibility curves indeed tend to disappear. However, whereas magnetoresistance properties are not significantly modified in the case of the layered manganites La 0 . 5 Sr 1 . 5 MnO 4 and LaSr 2 Mn 2 O 7 , huge magnetoresistance is induced in the case of the three-dimensional (3D) manganite Pr 0 . 5 Ca 0 . 5 MnO 3 . These strong modifications of the transport properties are discussed in the light of the magnetic properties.