Background: Investigating dental health knowledge among children is important. Knowing what behaviors are right in relation to dental health does not guarantee that children will practice those behaviors. However, lack of knowledge and misconceptions about dental health may lead to behaviors that are harmful to teeth and gum. Baseline data on knowledge levels are required to determine which particular areas of dental health education are in need of improvement for high-risk children living in different geographical areas. This research was conducted to study the oral health status, dental knowledge and behavior in relation to two different cities, among children in Baghdad and Thamar (republic of Yemen) governorate. Materials and Methods: The sample collected was composed of two geographically different groups, first group from Baghdad city: composed of 144 children and adolescents and the second group collected from the city of Thamar (republic of Yemen) composed of 108 of an age range 8-15 years old children. Dental plaque and Gingival health condition was assessed by using plaque index of Silness and Loe (1964),and gingival index of Loe and Silness (1963), Ramfjord index teeth were examined to represent the whole dentition. Oral examination was performed by a single examiner using mouth mirror and dental explorer for each child. Ten questions were fabricated to evaluate the dental health knowledge and behavior of the two groups. Results: This study was recorded that the age group 12-15 years old the significant difference was found in relation to gingival health condition, the dental Knowledge and behaviors was the highly significant difference was found between Baghdad and Thamar group. As well as highly scores of dental knowledge and behavior was significantly related to the dental plaque for both Baghdad and Thamar group. Conclusion: The difference in the geographical location could affect on oral hygiene, dental health knowledge and behavior of the children and adolescent.