Background and Purpose: Diadochokinetic skills (DDK) are thought to reflect speech motor competence. However, there is limited information concerning DDK performance in children with speech difficulties (SD) and how it relates to performance on other speech measures. The main purpose of this study was to investigate relationships between DDK accuracy, consistency and rate and measures of speech and oro-motor skill. A related aim was to identify whether there are distinct DDK profiles that map onto proposed subgroups of speech difficulty such as Developmental Verbal Dyspraxia (DVD). Method: Forty children with SD in the age range 4;0-7;11 were assessed on DDK tasks involving a range of stimuli types and lengths, along with a battery of speech and oro-motor assessments. The children’s performance was compared to that of forty age-matched typically-developing (TD) children. Results: The children with SD performed more poorly than the TD group on all three DDK measures. DDK accuracy correlated strongly with accuracy on speech output tasks and on an input task of mispronunciation detection. DDK consistency correlated with consistency on a single-word naming task. No correlation was found between DDK rate and other speech tasks. Furthermore, no relationship was found between DDK performance and oro-motor skills. Six distinct DDK profiles were identified in the group of children with SD but there was no robust evidence that these profiles map onto the subgroups of speech difficulty that have been proposed in the literature. Conclusion and Implications: DDK skills should be assessed and evaluated in the context of performance on other speech tasks. Theoretical implications are discussed and recommendations for clinical practice are made regarding methods for administering DDK tasks. There was little support for DDK being a unique marker of DVD, rather it appeared to be a marker of speech difficulties in general.