Lutetium and ytterbium isotopes with masses A=159,158 have been produced by proton induced spallation reaction, and investigated by on-line mass separation and subsequent decay spectroscopy. A new isotope¹⁵⁹Lu (T_1/2=12.3±1 s) has been identified, and new γ-ray data have been obtained for the decay of¹⁵⁸Lu and^{159, 158}Yb.