Electron attachment processes in isolated molecules in the gas phase, in clusters and in molecules condensed on surfaces are reviewed, and a special section is dedicated to electron attachment to biologically relevant molecules. For isolated molecules in the gas phase the emphasis is on the comparison between direct dissociation from strongly repulsive σ* states and the more indirect predissociation processes associated with the initial occupation of a π* MO. These processes are discussed with regard to the temperature dependence of the dissociative electron attachment processes and with regard to its high bond selectivity. Specific examples of high bond and site selectivity at particular electron incident energies are discussed in terms of thermo-chemically controlled and state controlled selectivity of the dissociative electron attachment process. Different processes that are specific for electron attachment to molecules in clusters or condensed on surfaces are discussed for prototypical cases. These include suppression and enhancement of DEA channels, negative ion formation through “electron/exciton-complexes”, scavenging processes, and low energy electron induced synthesis in thin molecular films and in clusters. Finally we discuss gas phase electron attachment to the DNA and RNA building blocks, i.e., the nucleobases, the sugar unit and the phosphate group. The relevance of these gas phase experiments to actual DNA damage such as single strand breaks is discussed and first gas phase electron attachment experiments on larger DNA units are discussed.