Background & Objective: Stuttering is a prevalent disorder in children and adolescents. Because attention is the only fuel resource for cognitive functions and the language have high cognitive functions, then it is possible that speech difficulties are related to attention deficit. The purpose of this study was to investigate the attentional demand of speech in children and adolescents with developmental stuttering. Materials & Methods: It is a dependent measurement study though which 30 school students (8-13 yr.) were selected by convenience sampling and speech therapist´s detection from Shahriyar. The instruments were used in this research consist of: a text for reading, a device for recording of speech, and stuttering severity instrument-3 (SSI-3). The research was implemented in two conditions: single task (only reading) and dual task (reading along finger tapping task). The data were analyzed using T- test. Results: Findings show that stuttering severity increased in dual task condition (divided attention). Conclusion: This result suggests that a decreased attentional capacity in children with developmental stuttering cause an increase in the number of stuttering words. With a better understanding of attentional functions of stuttering people as an important cognitive variables, we can take a step toward recognizing cognitive vulnerability of disorder. Therefore, intervention programs for children with developmental stuttering should pay attention to cognitive deficits and prior to speech interventions, the cognitive deficits should be eliminated with neuropsychological implements. With the improvement of neurological base of speech which is the first point of that in the brain, the considerable improvement may be seen in the stuttering severity.