Acetylcholinesterase (AChE) inhibitors are widely used in Alzheimer’s treatment, but they are also crucial for their action on organophosphorus insecticides. The latter exert their toxicity by inhibiting the AChE enzyme in insects, leading to their death. Amaryllidaceae alkaloids have been proven to be potent AChE inhibitors. In the present study methanolic extracts and essential oils being obtained from species of Asteraceae, Lamiaceae, Brassicaceae and Amaryllidaceae were evaluated in vitro for AChE inhibitory activity. Ellman’s colourimetric method, with modifications, was used for AChE activity evaluation. According to the activity level, the tested plant products were divided into three categories. First: plant products with strong activity comparable to that of galanthamine; second: plant products with medium activity, with IC50 value about 1 mg/ml and the last group with low activity, with IC50 value greater than 1 mg/ml. Essential oils of Origanum vulgare subsp. hirtum Ietswaart., Satureja pilosa Vel., Monarda fistulosa L., Thymus longedentatus (Degen & Urum.) Ronniger and the methanolic extract of Leucojum aestivum L. showed the most potent activity and were referred to as the first group. Carvacrol was identified as the main component of the most active essential oils. In L. aestivum extract, galanthamine was found as the main alkaloid. The obtained results indicate that essential oils and alkaloid-rich plant extracts possess the strongest AChE inhibitory activity. This gives us a reason to recommend these plant products to be tested for insecticidal activity in the future.