Luzula sect. Luzula is the most taxonomically diverse group within the genus. It displays a wide range of chromosome numbers due to polyploidy and agmatoploidy. In eight taxa of the section from Slovenia, NE Italy and S Austria, chromosomes were counted and the nuclear DNA amount, expressed as the C-value, was measured in root tip cells of seedlings, using interphase-peak DNA image cytometry. Previously known karyotypes were confirmed (Luzula campestris (L.) DC. subsp. campestris: 2n = 12 AL; L. multiflora (Ehrh.) Lej. subsp. multiflora: 2n = 24 AL and 2n = 36 AL; Luzula divulgata Kirschner: 2n = 24 AL; L. sudetica (Willd.) Schult.: 2n = 48 CL; and L. alpina Hoppe: 2n = 12 AL + 24 BL), and a new karyotype 2n = 24 BL was found in the region. Two new taxa were discovered and described: L. exspectata Bačič & Jogan (2n = 24 BL) and L. divulgatiformis Bačič & Jogan (2n = 24 BL). The 2C-value proved to be similar in diploid (L. campestris) and agmatoploid taxa (L. sudetica, L. exspectata, L. divulgatiformis) and ranged from 0.83 to 0.97 pg DNA. In the case of true polyploidy, the nuclear DNA amount approximately doubled in the tetraploids L. divulgata and L. multiflora (2C-value 2.09 and 1.88 pg, respectively) and tripled in hexaploid L. multiflora (2C-value 2.73 pg). The 2C-value of 2.06 pg of the partial agmatoploid L. alpina approximately equals the DNA amount in true tetraploids.