Several studies have demonstrated that children with poor reading comprehension abilities have weak expressive writing skills too. The aim of the present research was to establish whether poor comprehenders’ low performance in expressive writing is mediated by the need to produce relevant inferences to construct the narrative. To do so, we compared two conditions: in one, the children's comprehension of the story relied partly on their ability to draw crucial causal inferences; in the other, all the information needed to follow the sequence of events was provided in pictures. Irrespective of the condition, poor comprehenders (aged 8–10 years) produced less effective written texts. Analyzing the use of connectives shed some light on the characteristics of the poor comprehenders’ written narratives, which seemed to be less cohesive. The poor comprehenders tended to use more additive connectives than causal connectives, which is why their texts resembled a list of events with a description of each picture.