Source-specific conditional distributions of the duration of ground motion anticipated at a set of representative sites in New Zealand are computed using a procedure based on the generalised conditional intensity measure (GCIM) framework. Sites in the eastern part of the North Island and the northern part of the South Island are shown to be susceptible to long duration ground motions produced by large magnitude interface earthquakes in the Hikurangi subduction zone. Nevertheless, relatively short duration ground motions produced by lower magnitude earthquakes on adjacent crustal faults are still the primary contributors to their seismic hazard. Hence, an appropriate mix of short and long duration ground motions should be selected when assessing the performance assessment of structures located at these sites. Failure to consider hazard-consistent duration targets in addition to conditional spectra during record selection is likely to result in biased structural response estimates.