On May 20th 2012 (Sunday) an earthquake (ML 5.9) hit Northern Italy at 02:03 UTC,. The National Seismic Network [Amato and Mele, 2008; Delladio, 2011] of the Istituto Nazionale di Geofisica e Vulcanologia (INGV) located the hypocenter below the Po Valley in the Emilia region (44.89° N, 11.23° E, 6.3 km depth). Just after the mainshock, the INGV structure of rapid response for seismic emergency has been activated in order to install a temporary seismic network as a complementary of existing permanent network in the epicentral area. The INGV installed 44 temporary stations, ten of these transmitting in real time to seismic monitoring room in Rome. Further 38 temporary seismic stations (16 provided by National Civil Protection Department - DPC, 8 provided by the National Institute of Oceanography and Experimental Geophysics - OGS and 14 provided by French colleagues) have been installed in the epicentral area. The final configuration was obtained by coordination among INGV and other agencies. The Centro Operativo Emergenza Sismica (COES) [Moretti et al., 2010a] was activated relatively late, on June 8th 2012, because the INGV branch in Bologna located close to the epicentral area, was in the early days fulfilling the COES tasks. The COES ensured continuous and direct communication with the DPC officers present in the epicentral area. At the same time, the structure has been proposed as logistic support to all the INGV colleagues engaged in activities in the epicentral area (mobile seismic networks, EMERSITO, GPS, EMERGEO, QUEST) and to the service dedicated to the education and information promoted in favor of affected populations, civil defense operators as well as rescue volunteers. In this paper we will describe the activities carried out during the first month of emergency, the method and timing of the intervention, and finally the structures involved.