Supply web based Life Cycle Assessment (LCA) was used to assess environmental impacts of Elovena oat flakes, produced by RavintoRaisio in Finland. Data for the system model were acquired from the field, as empirical investigation of the real processes, thus providing a reliable basis to analyse the sources of environmental impacts ( hot spots ) and to consider respective improvement possibilities. The assessment took account of all stages of the most important product and distribution systems of oat flakes concerned from the production of farm inputs and raw material to the retail stores and, finally, to the porridge consumed. The environmental load from farm operations was the primary cause for global warming, eutrophication, acidification and photochemical ozone creation potential in production chain. However, traditional porridge cooking caused multiple carbon dioxide emissions compared to the production chain of flakes. Most of the environmental impacts of the system can be affected by choosing the porridge cooking method. The air emissions of porridge cooked in microwave were essentially smaller than when using traditional electric hot plate. The study generated knowledge improving the efficiency of production chain, which can be used as a basis for product improvement measures in the long term and according to the goals of sustainable development. Some improvements have been made in the production chain. Biogas has replaced heavy fuel oil in the generation of steam used for producing oat flakes. This change almost halved the volume of sulphur dioxide emissions in the entire production chain. Katajajuuri, J.-M. et al. 2003. Environmental impacts of oat flakes. Maa- ja elintarviketalous 33. 48 p. In Finnish. http://www.mtt.fi/met/pdf/met33.pdf. ISSN 1458-5081. ISBN 951-729-802-1.