Left hemisphere dominance has been established for use of single familiar tools and tool/object pairs, but everyday action in natural environment frequently affords multi-step actions with more or less novel technical devices. One purpose of our study was to find out whether left hemisphere dominance extends to such naturalistic action. Another aim was to analyze the cognitive components contributing to success or failure. Patients with LBD and aphasia, patients with RBD, and healthy controls were examined on experimental tests assessing retrieval of functional knowledge from semantic memory, inference of function from structure, and solution of mechanical and non-mechanical multi-step problems, and were confronted with two naturalistic tasks involving technical devices: preparing coffee with a drip coffee maker and fixing a cassette recorder. Both patient groups were about equally impaired on both naturalistic actions. Analysis of the experimental tests and their correlations to naturalistic actions suggested that different cognitive deficits caused failure in both patient groups, and that in LBD patients there were also different causes for failure on both naturalistic actions. The main difficulty of RBD patients seemed to reside in the demand to keep track of multi-step actions. In aphasic LBD patients difficulties with making coffee but not the cassette recorder were correlated with aphasia and defective retrieval of functional knowledge from semantic memory, whereas the cassette recorder correlated more strongly with a test probing solution of multi-step mechanical problems. Inference of function from structure which had been shown to be important for use of single familiar tools or tool/objects pairs [Goldenberg, G., Hagmann, S. (1998). AT Tool use and mechanical problem solving in apraxia. Neuropsychologia, 36, 581-589] appeared to play only a subordinate role for naturalistic actions involving technical devices.