  Quantum branching programs (quantum binary decision diagrams, respectively)
are a convenient tool for examining quantum computations using only a
logarithmic amount of space. Recently several types of restricted quantum
branching programs have been considered, e. g. read--once quantum branching
programs. This paper considers quantum ordered binary decision diagrams
(QOBDDs) and answers the question: How does the computational power of QOBDDs
increase, if we allow repeated tests. Additionally it is described how to
synthesize QOBDDs according to Boolean operations.
