I present results on non-perturbative effects in the c=1 string theory. First, I describe a geometric picture found in the CFT framework which gives an interpretation of D-branes in non-critical strings in terms of a complex curve associated with any closed string background. I show that its c=1 limit is degenerate and the degeneracy can be removed by considering a condensation of tachyon modes. Using the matrix model description, I calculate the leading as well as the subleading non-perturbative corrections to the string partition function. We find them by using the Toda integrable structure and from the realization of 2D string theory in terms of free fermions. Both methods give the same result which is also interpreted through correlation functions of a bosonic field. The leading corrections can be interpreted in terms of localized D-branes, whereas the sub-leading ones do not have a simple D-brane description.

Utrecht