[Full-text not avalaible yet]Two-dimensional photonic crystal lasers have been fabricated on III–V semiconductor slabs. Tuning of the spontaneous emission in micro and nanocavities has been achieved by accurate control of the slab thickness. Different structures, some of them of new application to photonic crystal lasers, have been fabricated like the Suzuki-phase or the coupled-cavity ring-like resonators. Laser emission has been obtained by pulsed optical pumping. Optical characterization of the lasing modes have been performed showing one or more laser peaks centred around 1.55 μm. Far field characterization of the emission pattern has been realized showing different patterns depending on the geometrical shape of the structures. These kinds of devices may be used as efficient nanolaser sources for optical communications or optical sensors.A.R. Alija thanks a FPU fellowship AP2002-0474 and L.J. Martínez an I3P fellowship. The authors would also like to acknowledge support from European Network of Excellence IST-2-511616-NOE (PHOREMOST) and NMP4-CT-2004-500101 (SANDIE), Spain-Italy Integrated Action HI2004-0367/IT2304, projects NAN2004-08843-C05-04, TEC-2005-05781-C03-01, NAN2004-09109-C04-01, CONSOLIDER-Ingenio 2010(CSD2006-00019), TEC2004-03545 and CARIPLO Foundation.Peer reviewed