The interplane spin cross relaxation time Tx measured by high frequency ESR in X-ray irradiated κ-(BEDT-TTF)2Cu[N(CN)2]Cl is compared to the interplane resisitivity ρ⊥ and the in-plane resistivity  ρII  between 50 K and 250 K. The irradiation transforms the semiconductor behavior of the non-irradiated crystal into metallic. Irradiation decreases Tx, ρ⊥ and ρII  but the ratio Tx/ρ⊥  and ρ⊥/ρII   remain unchanged between 50 and 250 K. Models describing the unusual defect concentration dependence in κ-(BEDT-TTF)2Cu[N(CN)2]Cl are discussed.