The present paper includes the results of the three weeks combustion tests with Greek lignite performed in the 1 MWth pulverized coal combustion facility of RWE-Power, in Germany. Overall scope of this campaign was to investigate the combustion behaviour, i.e. ignition, burnout and emissions, as well as the slagging and fouling tendency of Greek lignite under varying levels of inserted vapor. The utmost goal, when adjusting the vapor volume flow was to simulate the conditions within a real scale boiler, when raw lignite is substituted by dried coal of the same origin. Short and long term tests were carried out in the test facility and the fuel mass flow, the inserted vapor and flue gas volume flow and the furnace temperature were the main parameters. During all the tests, profile temperature and emission measurements were accomplished, while fly and bottom ashes were sampled and characterized. In the long term tests, the slagging and fouling tendency was estimated through the installation of dedicated deposition probes in four different temperature ranges within the furnace. Based on the experimental results, the anticipated increase of the furnace temperature profiles by decreasing the inserted vapor amount was confirmed. No significant trend on the CO and NOx emissions was observed in the most cases, while the operation modus appears to have a moderate effect on the deposition behaviour of Greek lignite. These preliminary investigations indicate that no significant operational problems will arise during the demonstration of raw and dried lignite co-firing in a large scale boiler.