The present invention relates to a process for the preparation of hydrothermal hybrid material, in particular coal-like hybrid material from biomass. The process involves the heating of a reaction mixture comprising water, biomass and a copolymerizable compound, wherein the copolymerizable compound is added when preparing the reaction mixture, in a variant of the process, the biomass is converted to activated biomass in a first step, and the copolymerization of the activated biomass and a copolymerizable compound to give the hydrothermal, preferably coal-like, hybrid material is started by adding a polymerization initiator. The invention also relates to the hydrothermal hybrid materials obtainable by the processes as such, e.g. to aqueous dispersions thereof. By incorporating copolymerizable compounds, e.g. petrochemical compounds in the structure of the hydrothermal hybrid materials, the physical properties of the materials and the preparation process thereof can be controlled.