Llano Bonito (area: 1,800 ha, altitude: from 1,180 to 2,120 m. asl) is a productive coffee-growing watershed within Tarrazú region of Costa Rica - reputed for its favourable growing conditions and high quality coffee. The majority of small-holders in the watershed produce coffee intensively in various shade forms - under single or mixed shade tree species as well as un-shaded, full sun-grown mono-crop. The knowledge base about site conditions (altitude, aspect and slope), shade trees, coffee plants and their interactions is lacking in Llano Bonito. To understand interactions between site conditions, shade trees and coffee plant characteristics, 95 sampling points were randomly selected in coffee fields of 37 representative farmers - spread all over the watershed, representing major variables of site conditions,. At each sampling point, site conditions were recorded, and shade tree and coffee plant characteristics were measured in nested square plots (100 m2 for shade trees and 25 m2 for coffee). At each sampling point, site characteristics were recorded, shade tree species were identified and their diameter at breast height (DBH) was measured in all shade trees above 10 cm DBH within the plots. The distance between coffee plant and rows were also measured. Inspection of data indicates the sample sites represented local diversity of site factors - altitudes from 1,365 m. asl to 1,940 m. asl, slopes from 0% to 100% and aspects from 150 to 3600. The total number of measured trees was 508, corresponding to a density of 535/ha. The average basal area at DBH was about 8.13 m2/ha. The number of species recorded was 16, most of which were represented by only a few individuals. The most frequent species were Erythrina spp. (224 individuals), Musa spp. (207 individuals) and Persea americana (34 individuals). When plots were categorized into un-shaded and shaded, and different types of shades within shaded based on dominant shade tree species, four categories of plots were identified- erythrina (45), banana (26), mixed shade (12) and unshaded (12). The average density of coffee shoots was 6,530/ha (min 3080, max 11,150). Results showing relationships between site factors, and characteristics of shade trees and coffee plants are presented as first step towards diagnosing coffee agroforestry systems of Llano Bonito watershed, Costa Rica.