Preliminary observations on the ecology of sessile oak (Quercus petraea (Matt.) Liebl.) seedlings.—The responses of sessile oak seedlings to four different light intensities and to increasing drought (three soil moisture contents) have been investigated in a nursery experiment in order to improve the knowledge of the ecology of this species in the Mediterranean area. Data have been compared with observations on natural regeneration established in different shade and soil moisture conditions in a sessile oak stand. The results of the two experiments showed that low light intensities (transmittance <5%) did not limit the seedlings establishment but induced lowest growth rates, while in full daylight seedlings mortality was very high (61%). In accordance with the observations in natural conditions, seedlings showed the best performances at intermediate light levels (50–80% of full daylight) and with increasing soil moisture: mortality was very low and average height increment, dry weight, relative growth rate (RGR) and net assimilation rate (NAR) showed the highest values. The differences in specific leaf area (SLA), leaf area ratio (LAR), root/stem ratio enabled to discuss the sessile oak seedlings ecology and adaptations to different light intensities and soil moisture content.