Background and Aim: Asking questions is one of the basic skills for getting information. "What", "Who", "Where", "Why", "How much", "How, etc. are question words frequently used for asking questions. Studies on the sequence of acquisition of question words in English speaking children follow a unique sequence. "What" is the first question word used by these children. We aimed to study whether Persian speaking children follow a unique pattern in the acquisition and use of question words as well.
Case: Two normal Persian speaking children (a boy and a girl) who were sent to the kindergarten of Faculty of Rehabilitation Sciences, Iran University of Medical Sciences by their parents were investigated. Children's spontaneous speech from 12 to 36 months was videotaped, and question words were extracted from phonetic transcription of both children's speech. In order to ask a question, both children initially used rising tone with /m/ or /hum/ before saying the first question word. Two first question words were "what" and "where" in both children's speech samples. Asking about the time with the question word /when/ was not appeared in their speech samples until 36 months. These two Persian speaking children also used Wh-question sequentially.
Conclusion: The result of this study was consistent with the results of other studies on English speaking children.

Background and Aim: Studies have shown that most children before age 4 are able to comprehend and express wh-question. In the Persian language, a case study has confirmed these results. The aim of this study is to evaluate the ability of 4-6 year olds to comprehend and express wh-question.
Methods: Seventy two 4-6 year-old Persian-speaking children were selected randomly. Wh-words consist of: what, where, who, why, and when. In the part of comprehension subjects answered questions about two pictures, and in the part of expression they asked questions elicited by a speaking puppet about four pictures. Descriptive analysis and student&aposs t-test were used for data analysis.
Results: In comprehension 4-6 year-old children gained the complete score (2) with SD=0 in all wh-words. However, 4-5 year old children gained the score of 1.89 with SD of 0.32 for the word when. In expression, independent t-test showed the maximum score of 3.52 with SD of 0.84 related to questions with who. 5-6 and 4-5 year old subjects had significant differences in questions with what (p=0.005), where (p=0.003), who (p=0.012), and when (p<0.001). Most errors were expressed in question with when.
Conclusion: Subjects of this study had the ability to comprehend and express wh-words. Comprehension of wh-words is easy for 4-6 year-old children they are able to use them in questions, but have some application errors.