Corporate strategic decisions are affected by investment opportunities and actions of rival firms. Imai and Watanabe suggest a real option and game theory model to determine optimal investment decision considering a two firms multistage game following a multiperiod trinomial process in a discret model. Imai & Watanabe model is used to define this optimal time to invest in a new tecnology as a function of the cost of investment and initial demand. We consider two competing firms in the Brazilian telecommunication market where one firm is leader (L) and the other is the follower (S). We assume both firms are already active in this market and intend to invest in a new technology that will allow them to expand their business. We define a trigger curve of cost of investment and initial demand of the services that define optimal investment strategy for the leading firm.