Purpose. - To investigate the frequency of post lumbar puncture headaches (PLPH) after diagnostic lumbar puncture (LP) and to search for influence factors. Patients and methods. - Conducted over 6 months into 8 paediatric services, the study concerned 2 to 15 years old children. The LP technic (cannula gauge, bevel orientation, child position, reinsertion of the stylet) was standardised. For each child questionnaires were filled with the parents 3 and 8 days after LP for inquiring headaches, postural characteristics, length and clinical consequences. Results. - Among 84 charts, 71 were exploitable. PLPH were observed in 25% of children. The mean duration was 5.9 days, mean bed rest was 1.4 day and mean antalgic treatment 1.7 day. The frequency of PLPH was not significantly influenced by age and sex, neither by the qualification of the physician performing the LP. The frequency was significantly lower when LP execution was easy (19.6 vs. 46.7% ; P < 0.05), and when the child had viral meningitis (8 vs. 34.8% ; P < 0.05). Conclusion. - We have found a more important frequency of PLPH than in previous paediatric studies. Clinical consequences justify other researches to precise influence factors and reduce the frequency of this complication. To investigate the frequency of post lumbar puncture headaches (PLPH) after diagnostic lumbar puncture (LP) and to search for influence factors. Patients and methods. - Conducted over 6 months into 8 pediatric services, the study concerned 2 to 15 years old children. The LP technic (cannula gauge, bevel orientation, child position, reinsertion of the stylet) was standardized. For each child questionnaires were filled with the parents 3 and 8 days after LP for inquiring headaches, postural characteristics, length and clinical consequences The mean duration was 5.9 days, mean bed rest was 1.4 days and mean antalgic treatment 1.7 days. The frequency of PLPH was not significantly affected by age and sex, neither by the qualification of the physician performing the LP. The frequency was significantly lower when LP execution was easy (19.6 vs. 46.7%; P <0.05), and when the child had viral m Conclusion. - We have found a more important frequency of PLPH than in previous pediatric studies. Clinical reactive justify other researches to precise influence factors and reduce the frequency of this complication.