This research was carried out to find out the nursing diagnoses in patients who have mechanical ventilation support in a respiratory intensive care unit. The study was conducted with 51 evaluations of critically ill adult patients who underwent invasive and non-invasive mechanical ventilation therapy in 2008. Data collection was based on Gordon's 11 Functional Health Patterns, and nursing diagnoses were determined according to North American Nursing Diagnosis Association-International (NANDA-I) Taxonomy II. The nursing diagnoses were determined by two researchers separately. The consistency between the nursing diagnoses defined by the two researchers was evaluated by using Cohen's kappa (kappa). Forty men (78.4%) and 11 women (21.6%) whose mean ages were 70.19 (SD = 8.96) years were included in the study. Nineteen subgroups of nursing diagnoses about safety/protection domain, and 15 subgroups about activity/rest domain were seen at different rates in the patients. There was a statistically significant difference between mechanical ventilation via tracheostomy or endotracheal tube and decreased cardiac output (d.f. = 1, chi(2) = 4.760, P = 0.029). The relationship between the length of time under mechanical ventilation and impaired physical mobility was considerably significant (d.f. = 3, chi(2) = 24.459, P = 0.000). It was found out that there was a high degree of agreement (96.8%) between the nursing diagnoses defined by the two researchers separately (kappa = 0.936, SE = 0.08).