Improved pulse sequences DIFN (abbreviation of the words: DIFferentiation by N pulses), 90 o - τ 1 - 180 o - τ 1 - ... 180 o - τ n , with optimised time intervals τ 1 for T 1 measurement and contrast enhancing in NMR imaging are presented. The pulse sequences DIFN have a better sensitivity to T 1 than the well-known pulse sequence SR. In contrast to the IR pulse sequence, the information given by the DIFN pulse sequence is more reliable, because the NMR signal does not change its sign. For a given time interval τ 0 =< (0.1 - 0.3) T 1 ' the DIFN pulse sequences serve as T 1 -filters. They pass the signal components with relatively short T 1 < T 1 ' and suppress the components with relatively long T 1 < T 1 '. The effects of the radiofrequency field inhomogeneity and inaccurate adjusting of pulse lengths are also considered. It is also proposed in this work to use the joint T 1 T 2 -contrast in NMR imaging obtained as a result of applying the DIFN pulse sequences in combination with the well-known Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence. The region of interest, where the contrast should be especially enhanced, is specified by the two times at which measurements are performed, which allow the amplitudes of pixels to reach some defined levels by spin-lattice and spin-spin relaxation.