Sustainable development is a key principle in regional planning in Europe, but its implementation faces challenges due to vague definitions and conflicting goals. Germany and Poland have integrated sustainable development into their planning laws and documents, but conflicts between ecological, social, and economic aims still exist. In Poland, new regional planning documents are being developed to align with the principle of sustainable development. The main focus is on goals like controlling urban sprawl, protecting open spaces, and improving mobility in the regions of West Pomerania (Poland) and North-Rhine Westphalia (Germany).