the purpose of this research was to assess the relation between mothers’ guidance speech and children’s participation in the problem-solving tasks. fifty mother-child dyads were videotaped during two joint problem-solving tasks. the children were aged between 3 and 5. the tasks were designed to elicit a didactic setting (the construction of a series of pieces of different lengths, with and without a model). the mothers’ speech was analysed according to its content, as per wertsch’s (1985) view of the semiotic devices that adults use to establish inter-psychological functioning (abbreviation and referential perspective), and considering metacognitive and cognitive mediation. the children’s participation was assessed on the basis of the extent to which they were responsible for solving the problem and was related to the mothers’ scaffolding speech, with consideration given to the variables mother’s formal schooling and the children’s cognitive and language development. the results reveal that the mothers adopted a general guidance speech script, but in the seriation with a model the metacognitive challenges were more frequent, while in the series without a model it was the cognitive mediation that was used relatively more often. however, there was no significant relationship between the discourse of the mothers who employed higher level metacognitive or cognitive challenges and the children’s participation in the tasks. these results are discussed in terms of the child and mother variables on the basis of the socio-constructivist perspective taken by karmiloff smith’s representational redescription model (1992).