The electronic emission spectra of LaH and LaD have been investigated in the 3 μm-700 nm spectral region using a Fourier transform spectrometer. The molecules were excited in a lanthanum hollow cathode lamp operated with neon gas and a trace of hydrogen or deuterium. The bands observed in the 1 μm-3 μm region have been assigned into two new electronic transitions; A 1Π-X 1Σ+ and d 3Φ-a 3∆. The LaH bands with origins at 4533.5593(8) cm-1 and 4430.1916(13) cm-1 have been assigned as the 0-0 and 1-1 bands of the A1Π-X 1Σ+ transition. The rotational analysis of these bands provides the following principal molecular constants for the ground X 1Σ+ state, Be=4.080 534(80) cm-1 and αe=0.077 39(10) cm-1 and re=2.031 969(20) Å. To higher wave numbers, three subbands of LaH with origins at 5955.8568(16) cm-1, 6238.3768(8) cm-1, and 6306.6757(15) cm-1 have been assigned as the 3Φ2-3∆1, 3Φ3-3∆2, and 3Φ4-3∆3 subbands of the d 3Φ-a 3∆ electronic transition. The rotational analysis of the 0-0 and 1-1 bands of the 3Φ2-3∆1 and 3Φ4-3∆3 subbands and the 0-0, 1-1, and 2-2 bands of the 3Φ3-3∆2 subband has been obtained and effective equilibrium constants for the spin components of the d 3Φ and the a 3∆ states have been extracted. Magnetic hyperfine structure was also observed in the a 3∆ state. The rotational analysis of the corresponding LaD transitions has also been carried out and equilibrium constants for the ground and excited states have been determined. The singlet-triplet interval between the X 1Σ+ state and the a 3∆ state is not known but on the basis of ab initio calculation and by comparison with LaF and YH, we believe that the ground state of LaH is a 1Σ+ state.