The possibility of synthesizing protonated derivatives of layered perovskite-like titanates Bi₄Ti₃O₁₂, ABi₄Ti₄O₁₅, (A = Ba, Sr, Ca) and K_2.5Bi_2.5Ti₄O₁₃ is experimentally investigated. It is established that in the case of Bi₄Ti₃O₁₂ and ABi₄Ti₃O₁₅, single-phased protonated derivatives cannot be obtained by treating the compounds with acid solutions, due to the partial dissolution of initial oxides, accompanied by the formation of titanium dioxide. In the case of K_2.5Bi_2.5Ti₄O₁₃ titanate, a number of new protonated and hydrated derivatives are obtained and described.