Manganese (Mn) acceptors are well known to form complexes with hydrogen (H) in InP and GaAs crystals. However, to our knowledge, the formation of such complexes in Gal? has not been reported yet. The difficulty in formation of Mn-H complexes in GaP can be explained by unfavorable mutual positions of H and Mn energy levels in GaP band structure. A series of Gal? samples intentionally doped with Mn and some of them co-doped with zinc (Zn) and containing also unintentional H and carbon (C) has been investigated. In very slightly p-type samples, a local vibration mode at 2369.4cm(-1) at 6K was found, which we ascribed to Mn-H complexes by comparison of energy positions corresponding to analogical ``Mn-H'' complexes in other semiconductors. In more strongly p-type samples, these complexes were not found but Zn-H and C-H complexes were present. (C) 2007 Elsevier B.V. All rights reserved.