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Seeded emulsion polymerizations of styrene in the presence of two reversible addition–fragmentation chain‐transfer (RAFT) agents were studied. We designed the seed to be small to observe the effects of exit and, we made the seed of poly(methyl methacrylate) so that the molecular weight distributions of poly(styrene) by gel permeation chromatography could be obtained independently by UV detection. The rates were significantly retarded by the presence of a RAFT agent, with the retardation being greater with an EMA RAFT agent [2‐(ethoxycarbonyl)propyl‐2‐yl dithiobenzoate] than with a cumyl RAFT agent (2‐phenylprop‐2‐yl dithiobenzoate). We propose that exit from the particles after fragmentation was the main cause of retardation. In addition, the number‐average molecular weight and polydispersities (broad) did not resemble the characteristic living behavior found in bulk or solution. This was a result of …