We describe a neglect patient who showed systematic transpositions of left-sided items onto the right side in clock drawing. When the patient had to write single hours on blank clock dials he again showed allochiria, while he copied single spatial locations without transpositions. The patient also showed a variable number of spatial transpositions on imaginal tasks with well known and novel material acquired through visual modality and on controlled constructional tasks, independently from response modality (verbal, graphic or motor). From this basis, we argued that spatial transpositions may derive from an impairment of the mental representation of space. Moreover, we speculated that such errors may result from cognitive conflict between different sources of information.