According to UNFCCC statistics, in 2015 Romania was the country in the European Union that reported the highest emissions of CH4 from the oil and gas sector to the atmosphere, in particular related to methane production and end use. Limiting these oil and gas-related emissions could provide an attractive greenhouse gas emission reduction target for the EU. The ROMEO project was designed to provide experimental quantification of methane emissions from the oil and gas sector in Romania and is part of the international Climate and Clean Air Coalition's (CCAC's) Methane Science Studies. The main ROMEO campaign took place in October 2019. Eight ground measurement teams visited more than 1000 individual facilities, whereas about 200 quantifications were attempted. The teams performed methane measurements by stationary and mobile measurements from vehicles, using tracer release approaches and by plume mapping from drones. An optical gas imaging team visited many facilities in order to inv estigate the origin of the emissions at the component scale. To connect the facility scale to the regional scale, two research aircraft performed more than 20 research flights to identify and quantify methane emissions from individual facilities, facility clusters and extended regions. Ground-based in situ and total column measurements provide additional information on the background levels of CH4. Various models are used for emission quantification, from plume dispersion and mass balance models for individual facilities to atmospheric chemistry and transport models for interpretation of the larger scale aircraft measurements. The final goal of ROMEO is to provide a combined bottom-up and top-down approach to quantify CH4 emissions related to oil and gas exploration, natural gas distribution and gas use from Romania. During the splinter meeting we will present the overall setup of the ROMEO project, interesting examples from individual facilities and preliminary results from ground and airborne measurements.