This paper focuses on the description of the structure and water-air properties of Grodan rockwool removed from the greenhouse after one production cycle of tomato. After removal from the greenhouse, the rockwool contained a lot of roots, the result of which was a considerable level of organic matter in the waste material, at 9.0 g/100 g. The analyses were conducted on rockwool crushed into scraps measuring 5×5, 2.5×2.5, and 1×1 cm. The used rockwool compared to new rockwool displayed a decrease in the container water capacity at water potential state of -0.98 kPa, and an increase in the field water capacity at water potential values of -9.81, -15.54, and -30.99 kPa. The highest gravimetric and volumetric water capacity at water potential of -9.81 kPa was noted for rockwool fragmented in large scraps, and at water potential values of - 15.54 and -30.99 kPa for rockwool crushed into medium scraps. These changes are favorable from the viewpoint of the possibility of utilizing waste rockwool for soil reclamation.