Introduction: Nocturia is categorized into many categories. Each category requires different approaches and treatment. We aimed to obtain data regarding nocturia, classified into categories according to its pathogenesis, in Thai patients. Methods: We reviewed 133 medical records and voiding diaries of the patients who attended a urologic clinic in a tertiary teaching hospital during year 2009-2010 with nocturia problems. Those data were analyzed to sort these nocturia patients into the appropriate categories. Results: There were a total of 133 patients, consisting of 94 males (70.1%) and 39 females (29.9%). Overall mean age was 64.74 ± 25.85 years. There was no statistically difference between the two genders (Male 65.94 ± 24.56 years vs. Female 61.87 ± 28.24 years, p = 0.10). Among these, 71 patients (53.4%) had nocturnal polyuria. Almost all patients (132 patients, 99.2%) met the criteria for diminished global/nocturnal bladder capacity. The younger patients (less than 40 years) were found to have more severe clinical symptoms than the older patients (6 from 8 or 75% vs. 46 from 125 or 36%, p = 0.032). Seventy patients (52.6%) met the criteria of Mixed NP and Diminished. There were 32 patients (24.1%) found in the group of Global polyuria. Only one patient was classified as isolated nocturnal polyuria and none as isolated global polyuria. Conclusion: Nocturnal polyuria and global polyuria are not uncommon conditions and most of these patients might have concomitant diminished bladder capacity for which investigation or simultaneous treatment may be needed to gain the best treatment result.