In this prospective study 37% of 239 patients developed a post-lumbar puncture headache (PPH) after a diagnostic lumbar puncture. PPH was more prevalent in females than males (46% vs. 21%; P = 0.0003) as were the severest form of PPH (64% vs. 23%; P = 0.02) and nausea (74% vs. 39%; P = 0.01) in those who developed PPH. Females scored their pain in the upright position more severe on a 100-mm visual analogue scale than males (median 60 mm vs. 47.5 mm; P = 0.02). The frequency of PPH was higher with the use of a 20-gauge compared with a 22-gauge needle in all patients (50% vs. 26%; P = 0.0002) and in females (57% vs. 36%; P = 0.02) and males (38% vs. 10%; P = 0.004), separately. Neither age, weight, height, nor body mass index (BMI), influenced the prevalence of PPH, but tinnitus was more prevalent in tall compared with smaller patients (53% vs. 17%; P = 0.02). Old age was associated with a long median pain delay upon rising, and also, small patients tended to report a longer median pain delay than tall patients. The pain intensity changed more slowly upon rising and reclining in patients with a high BMI than in those with a lower BMI (median 60 s vs. 12 s; P = 0.02). The results concerning height, BMI and needle size might be anticipated according to the leakage theory. In a multivariate analysis sex (P = 0.0003) and needle size (P = 0.0002) were related to the development of PPH on a statistically significant level. Furthermore, the pain severity was positively related to female sex (P = 0.03) and young age (P = 0.03). The pain delay increased with age (P = 0.008) and the pain decrease time increased with an increasing BMI (P = 0.04).