The invention relates to a process for preparing pressure-sensitive adhesives (PSAs) which have high molar masses in combination with a narrow molar mass distribution, and also to PSAs, especially polyacrylate-based PSAs, prepared accordingly. It has been found that, surprisingly, polymers with high molar masses and a narrow molar mass distribution, more particularly polyacrylates with high molar masses and a narrow molar mass distribution, can be prepared outstandingly in particular by means of RAFT processes in the presence of a diradical initiator which undergoes thermal cyclization to form a diradical, these polymers being suitable for use as high-shear-strength PSAs.