We discuss two examples of quantum systems with interactions supported on lines located in a plane. First, we analyze the model with delta potential supported on angle in $\R^2$. Our aim is to derive the eigenvalues asymptotics if the angle-shape line approach to the straight line. Moreover, we study the system with potential supported on two parallel lines and the eigenvalues asymptotics is obtained if both lines approach to each other. Finally, discussed some generalizations of the above mentioned systems. The results presented in the talk are based on the common works with P.Exner and D.Krejcirik.