The escape out of open quantum systems can be characterised by quasibound states, which are solutions of the wave equation subject to outgoing boundary conditions. The energy eigenvalue of a quasibound state is complex, and the imaginary part is associated to the decay rate of the state. Quasibound states can be observed, e.g., as the lasing modes of optical microresonators. Random-matrix theory gives a wealth of information on quasibound states in disordered media, such as random dielectrics. Interesting systems are, however, ballistic (clean), and scattering only takes place at the (often complicated) confinements. I discuss the similarities and differences between quasibound states in disordered and ballistic systems. A semiclassical analysis reveals that ballistic systems feature a set of quasibound states which decay very quickly (faster even than the classical time of flight). The remaining long-lived quasibound states obey random-matrix statistics, just as in disordered systems, but renormalized in compliance with a recently proposed fractal Weyl law. I illustrate these results numerically for a model system, the open kicked rotator.