The production of quality and healthy seedlings is one of the most sensitive parts of production. During the seedlings production, it is very important to prevent the appearance and spread of the most significant diseases and pests, because the plant is in the most sensitive period of its life. In the research, seedlings were grown conventionally in polystyrene containers and hydroponically in a floating system. By comparing these two growing technologies, seedlings of different morphological traits were obtained, with the simultaneous possibility of monitoring the appearance of pests and diseases during the seedlings production. In conventional cultivation, the seedlings were shorter, have less biomass, fewer developed leaves and less leaf area. Seedlings from hydroponic cultivation were longer, with higher biomass and a better developed root system, as well as a higher number of leaves with a larger leaf area. Also, the leaves of hydroponically grown seedlings were darker green. From the results, it can be concluded that due to their development, hydroponically grown seedlings were ready for planting earlier than conventional ones, which means that it is possible to shorten the production cycle. During the hydroponic production of seedlings, the appearance of cabbage moth and cabbage leafhoppers was observed, and to a lesser extent, seedling damping off disease and cabbage blight. Although the listed harmful organisms have been successfully controlled by using chemical protection measures based on monitoring, it is necessary to consider the use of other methods of control as well as the use of plant protection agents through nutrient solution.