A process for the pyrolytic depolymerization of a styrene-containing plastics waste consisting of the components A, B1, B2, B3 and C: A: 10 to 100% by weight, based on the entirety of components A, B1, B2 and B3, of at least one styrene-containing polymer comprising at least 40% of styrene, preferably at least 50% by weight of styrene, particularly preferably at least 80% by weight of styrene, in particular at least 85% by weight of styrene, based in each case on component A, and up to 60% by weight, based on component A, of rubber and/or other comonomers which do not interrupt the pyrolysis process, in particular acrylonitrile, vinyl chloride, methyl methacrylate and/or alphamethylstyrene; B1: 0 to 60% by weight, based on the entirety of A, B1, B2 and B3, of polyolefin or polyolefin mixtures, such as polyethylene or polypropylene; B2: 0 to 60% by weight, based on the entirety of A, B1, B2 and B3, of other polymers, differing from A and B1, for example polycarbonates, polyesters, polyamides and/or polyvinyl chloride; B3: 0 to 20% by weight, based on the entirety of A, B1, B2 and B3, of conventional plastics additives and conventional plastics auxiliaries; C: 0 to 50% by weight, based on the entirety of A, B1, B2 and B3, of other foreign substances, dirt and moisture; comprising the following steps: i) decomposing the styrene-containing plastics waste in a suitable reactor without a catalyst via introduction of thermal energy and optionally of shear energy, where the plastics waste to be decomposed is introduced into a pyrolysis zone of the reactor and is pyrolyzed there at a temperature of 250°C to 500°C (average material temperature of the reaction mixture measured at the inner surface of a reactor wall during the reaction time), where the residence time in the pyrolysis zone of the plastics waste to be pyrolyzed is 1 to 45 minutes, and where the styrene component of the styrene-containing plastics waste is at least partially decomposed to give styrene monomers and styrene oligomers; ii) discharging and collecting the gases produced in step i) and condensation of the low-molecular-weight products comprising the resultant styrene monomers, in a suitable separator; iii) separating, by means of fractional distillation, of the condensed low-molecular-weight constituents of the previous step comprising the resultant styrene monomers. A: 10 to 100% by weight, based on the entirety of components A, B1, B2 and B3, of at least one styrene-containing polymer comprising at least 40% of styrene, preferably at least 50% by weight of styrene, particularly preferably at least 80% by weight of styrene, in particular at least 85% by weight of styrene, based in each case on component A, and up to 60% by weight, based on component A, of rubber and/or other comonomers which do not interrupt the pyrolysis process, in particular acrylonitrile, vinyl chloride, methyl methacrylate and/or alphamethylstyrene; B1: 0 to 60% by weight, based on the entirety of A, B1, B2 and B3, of polyolefin or polyolefin mixtures, such as polyethylene or polypropylene; B2: 0 to 60% by weight, based on the entirety of A, B1, B2 and B3, of other polymers, differing from A and B1, for example polycarbonates, polyesters, polyamides and/or polyvinyl chloride; B3: 0 to 20% by weight, based on the entirety of A, B1, B2 and B3, of conventional plastics additives and conventional plastics auxiliaries; C: 0 to 50% by weight, based on the entirety of A, B1, B2 and B3, of other foreign substances, dirt and moisture; i) decomposing the styrene-containing plastics waste in a suitable reactor without a catalyst via introduction of thermal energy and optionally of shear energy, where the plastics waste to be decomposed is introduced into a pyrolysis zone of the reactor and is pyrolyzed there at a temperature of 250°C to 500°C (average material temperature of the reaction mixture measured at the inner surface of a reactor wall during the reaction time), where the residence time in the pyrolysis zone of the plastics waste to be pyrolyzed is 1 to 45 minutes, and where the styrene component of the styrene-containing plastics waste is at least partially decomposed to give styrene monomers and styrene oligomers; ii) discharging and collecting the gases produced in step i) and condensation of the low-molecular-weight products comprising the resultant styrene monomers, in a suitable separator; iii) separating, by means of fractional distillation, of the condensed low-molecular-weight constituents of the previous step comprising the resultant styrene monomers.