High-order multiplicity of PMS stars: results from a VLT/NACO survey S. Correia, H. Zinnecker, Th. Ratzka, M.F. Sterzik We will report on our survey for high-order multiplicity among wide visual Pre-Main Sequence (PMS) binaries conducted with NACO at the VLT. The sample is composed of 55 T Tauri systems from various star-forming regions, essentially composed of one or more CTTS components. Of these systems, 8 are found to be triple and 7 quadruple, three of those clearly being in a non-hierarchical configuration. The corresponding degree of multiplicity among binaries (number of triples or quadruples divided by the number of systems) is 28.6 +/- 8.3% in the separation range 10/14 AU - 1700/2300 AU, with the largest proportion from the Taurus cloud. The observed frequency is in relatively good agreement with current predictions from numerical simulations of star formation. Although of low statistical significance, comparison with previous multiplicity surveys in a common separation range tends to show that such high multiplicity frequencies among binaries are rather expected for samples dominated by systems with only WTTS components. We provide a first analysis of the CTTS vs. WTTS companion statistics within our systems. It is shown that one half are systems of mixed type (i.e. at least one component with a different type) and that most of the time the closest pairs are WTTS-WTTS pairs. A tentative explanation is that the common reservoir invoked for isolated pairs for replenishment of the individual accretion discs has been disrupted in those multiple systems.