  An open question about Gabidulin codes is whether polynomial-time list
decoding beyond half the minimum distance is possible or not. In this
contribution, we give a lower and an upper bound on the list size, i.e., the
number of codewords in a ball around the received word. The lower bound shows
that if the radius of this ball is greater than the Johnson radius, this list
size can be exponential and hence, no polynomial-time list decoding is
possible. The upper bound on the list size uses subspace properties.
