This paper presents the remediation works of surface openings in the Sisak-Moslavina county, whose activation was triggered by the M6.2 earthquake in December 2020, with an epicenter near Petrinja. In addition to the immediate vicinity of residential buildings, openings appear near the transport infrastructure, on cultivable and non-cultivable agricultural land and in the forests of the municipality of Donji Kukuruzari. Some of the openings are in the immediate vicinity of the Pašino Vrelo water well. The mentioned surface openings, appeared during and after the main impact, were identified as collapse sinkholes, the development of which was not indicated by any deformation of the ground surface or subsidence, which makes them extremely dangerous. The lack of surface indicators, along with the sudden increase in the number of sinkholes in the period after the earthquake, make this area highly risky for its inhabitants. As part of the assessment of the condition and categorization of the collapse sinkholes, which preceded the development of remediation design and remediation works, 143 sinkholes were detected, two of which stand out with large volumes of 943 and 5014 m3. The other sinkholes have a volume of less than 450 m3, with most of them having a volume of 1 - 50 m3. The paper presents the efforts in categorizing sinkholes to determine the priorities in remediation, development of remediation design based on the inverse filter method with the use of materials of different gradation and geosynthetic materials, as well as the remediation works and associated challenges.