The resonance lines of beryllium like and lithium like molybdenum have been observed in high-temperature JET tokamak discharges into which molybdenum was introduced using the laser blow-off method. The measured transition wavelengths are 2s2 1S0-2s2p1P1 49.904±0.03Å, 2s2 1S0-2s2p 3P1 137.787±0.03Å, for Mo XXXIX, and 2s2S1/2-2p2P1/2 143.998±02Å, 2s 2S1/2- 2p 2P3/2 58.499±0.02Å, for Mo XL. For the beryllium like ion the results are compared with the semiempirical predictions by Edlén, while the results for lithium like Mo are compared with the calculations by Johnson et al.