The contribution of this thesis is in providing a risk assessment for managing real estate investment. Property investment is subject to numerous specificities among which location, liquidity, investment size or obsolescence and requires active management. These specificities make the traditional approaches to measure the risk difficult to apply. We present in our research work in the form of four papers on the real estate portfolio or risk management evolving around the valuation of the risk with a particular emphasis on the value at risk models. This research builds upon the literature by relying on previous works examines first the implication of the options to vacate in favor of the tenant embedded in continental Europe commercial lease contract and their implication on the portfolio value, risk and management and second the valuation of value at risk measurements through two proposed new approaches.In the first paper we consider the options embedded in lease contract in order to better assess portfolio value and portfolio risk. This is attempted through the use of Monte Carlo simulation and option's theory. The second paper considers the holding period of a real estate portfolio when the break options are taken into account. The third paper proposes a model to determine the value at risk of an investment that considers the non-normality of real estate returns using Cornish Fisher expansion and rearrangement procedures. Finally in a fourth paper, we present a model we have specifically developed for real estate value at risk assessment and that account for the most critical parameters which influence property returns.