We have used photoemission spectroscopy to study the valence band structure of clean and in situ Cs intercalated VSe2. The results show that the valence band structure of VSe2 is transformed, from initially being of 3D character, to become essential 2D, as Cs is intercalated. The changes in the electronic structure are to a large extent understandable as caused by intercalation-induced de-coupling of the VSe2 layers, and electronic charge transfer from Cs to the host material. Comparison with band structure calculations supports this picture. Our findings indicate that the Cs/VSe2 system may be of great value in studies of "reduced dimensionality" phenomena.