Processes for high-level nets AE are often defined as processes of the low-level net Ð Ø ´AE µ which is obtained from AE via the well-known flattening construction. This lowlevel notion of processes for high-level nets, however, is not really adequate, because the high-level structure is completely lost. For this reason we have introduced in a previous paper a new notion of high-level net processes for high-level nets which captures the highlevel structure. The key notion is a high-level occurrence net Ã, which generalizes the well-known notion of occurrence nets from low-level to high-level nets. In contrast to the low-level case we consider high-level occurrence nets together with a set of initial markings of the input places. In this paper we show under which conditions the behavior of low-level occurrence nets and processes can be generalized to the high-level case. A key notion is the instantiation Ä of a high-level occurrence net Ã, where Ä is a low-level subnet of the flattening Ð Ø ´Ãµ with isomorphic net structures of Ä and Ã. One of our main results characterizes under which conditions a high-level occurrence net -and hence a high-level net process -has unique and nonoverlapping instantiations and can be represented by the union of all its instantiations.