To study a relationship between manganese nodule occurrence (type and abundance) and the thickness of uppermost transparent layer, nodules were collected at 37 stations using Free-Fall Grab sampler in the Korea Deep Ocean Study (KODOS) 98-1 area, northeast equatorial Pacific (127 degrees W-136 degrees W, 9 degrees N-17 degrees N, and high-resolution (3.5 kHz) seismic profiles were also charted in the study area. Sedimentary layer on the seismic profiles can be divided into the upper transparent layer and the lower opaque layer based on acoustic characteristics. Manganese nodules were classified into r-, s-, t-, and d-types depending on the surface texture. The acoustically-transparent uppermost sedimentary layer in the northern part of the KODOS 98-1 area is thicker than that in the southern part. The s- and t-type nodules are dominant in the northern part. The r-type nodules were collected mostly in the southern part which is characterized as abyssal plain, while the s-type nodules were produced in the northern part with many seamounts. Marginal nodule abundance of s-type manganese nodule decreases as the acoustically-transparent uppermost sedimentary layer thickens. S-type nodule shows the significant correlation between the marginal manganese nodule abundance and the thickness of the acoustically-transparent uppermost sedimentary layer.