Strategic alliances and mergers & acquisitions are theoretically now considered as real levers of value creation. This value creation takes different forms, essentially strategic value, substantial value, institutional value and financial value (including shareholders). This latter holds our attention specifically. The objective of our research, after analyzing the results of empirical works focused on the acquisition announcements impact on the stock market performance, is to answer two fundamental questions. The first question is to know that if, on a more or less distant horizon, the stock market performance of acquisitions coincides with the actual performance and so if this form of acquisitions can be justified by the financial motivation of CEOs or shareholders. The second question is to know that if this hypothesis is also true in the case of alliances, establishing by the way an advantageous comparison in favor of one or other of the external growth options. Our final results show that in the short term the announcement of an alliance has a negative impact on performance as opposed to the announcement of a merger & acquisition, while other hand on the long-term, there is no positive impact (neutral impact) on financial performance whether it be the strategic alliance or merger & acquisition. We explain this result by the phenomenon of "creation of compensatory value" in the context of a strategic and financial plan.
