The lifetimes of electrons injected into large (approximate to10(6) atoms) superfluid He-4 droplets have been measured in the presence of different prior embedded rare gas atoms, their clusters, and the molecules O-2, H2O, and SF6. For the light rare gas atoms Ne and Ar the lifetimes of about 6.10(-2) s, found previously for pure droplets, are reduced to between 1-2.10(-2) s. Single molecules with large electron affinities, such as SF6 and O-2 and small clusters of H2O lead to a significant increase in the lifetimes. In the case of Kr and Xe, larger clusters with (n) over bar >14 are needed before the lifetimes increase. A simple model, which takes account of the energy levels occupied by the electrons in the corresponding molecules or the clusters, assumed to be solid, can qualitatively explain the observations. (C) 2003 American Institute of Physics.