With a view to monitor the formal valence of copper in YBaCuO system, substitutions of divalent (Ca) and tetravalent (Pr) impurities at Y‐site have been carried out. In addition to this the cooperative effect of these substitutions at Y‐site on the structural and superconducting behavior of YBaCuO system has been investigated using X‐ray and susceptibility measurements. The changes in the superconducting transition temperature have been discussed in the context of oxygen content and changes in the formal copper valence in the YBaCuO system.