Ultrashort UV excimer laser ablation of materials shows several advantages over conventional UV excimer laser ablation. We describe new experimental results on lithium niobate, LiNbO3, using 308 nm pulses of 1 ps duration. The fluence threshold for material removal is reduced by one order of magnitude when compared with 16 ns pulses at 308 nm. In addition the etch rate is up to three times higher for picosecond pulses and it is independent of the diameter of the ablation area. We discuss a simple model describing the etching and ablation behaviour of materials upon interaction with UV excimer laser pulses of different pulse duration.