The invention concerns a rotor of an electrical machine, particularly a driving motor for a hermetically enclosed refrigerant compressor with a body (4) comprising a magnetically conductive material, the rotor having a plurality of axially extending slots (5, 6), which are filled with an electrically conductive material. It is endeavored to achieve a good performance. For this purpose, it is ensured that an extension section (7) of a first group of slots (5) extends further radially inwards than a second group of slots (6), and that between two slots (5) of the first group at least one slot (6) of the second group must be arranged, a first flow cross-section being formed between neighboring extension sections (7) at the circumferentially shortest distance (a) between the two extension sections (7), a second flow cross-section being formed between neighboring slots (5, 6) at the circumferentially shortest distance (b) between the slots (5, 6), the first flow cross-section corresponding to the sum of the second flow cross-sections between the two slots (5) of the first group.