Discount Cash Flow Analysis can be defined a well accepted real estate valuation methodology both by academicians and by professionals. Unfortunately behind this common term there are several differences both in terminology and in methodological application. This paper tries to compare a British Approach with a US approach to DCF (Achour Fisher,1999). Furthermore inside each approach the inputs may vary in a significant way. This variability affects the final result of valuation creating among the other problems of confirmation bias . For this reason a valuation guideline on DCF application may be helpful in order to rule out the differences in the application of the method. A further issue may be a harmonization between the two approaches in a globalized real estate market.