Background: Rapid technical development of Computed Tomography (CT) means usage the modern, fast scanners which possibilities are not always known by users. A common conviction is the high number of detectors is equivalent to an accurate investigation of sub-millimetre slices of patient body and detection of such small-size lesions. Aim of the paper was to compare an imaging possibilities of the two CT scanners of the same vendors which differ only the configuration of detectors in use. (The group of 48 rows of detector is physically the same for the both scanners.) Material/Methods: Quality of images was controlled using Catphan series 500. The high- contrast resolution, lowcontrast resolution and signal-to-noise ratio were evaluated for images recorded at the constant reconstruction thickness of 5 mm. Results: A precision of imaging was evaluated on the basis signal-to-noise ratio (SNR) in relation to CT Dose Index. The lowest SNR at satisfying visualisation of the low-contrast objects was slightly above 5. The corresponding CT Dose Index was over 5mGy. Care-dose option decreases SNR to nearly 2 what follows unacceptable visualisation of low-contrast objects. Conclusions: on the basis the results for the both scanners was found that high number of active detector rows help to achieve a better visualisation of low-contrast objects under condition of higher CT Dose Index values. The space resolution does not change with the detector configuration.